Forever bike. LOL. good one, you almost got me with that one.
I remember when ti came in and everyone came up with the forever bike concept.
Hell, why would anyone want a forever bike? I mean we live in a technologically galloping time. Improvements we can't even imagine, are just around the corner. Disc or rim brakes are the current question, but next week it will be some other upgrade or advancement and you, along with the rest of us, will be clamouring for it.
Your new bike will be a 5 year bike at best. Get used to that. Buy whatever suits your needs, ride it for 5 years, then put it on the Kickr and buy a new bike for the road. Repeat as necessary.

Sigh...I have a 30 year old road bike that I still ride regularly, AND has modern equipment on it (brand new wheels as of last week, new compact crankset, etc.)

Prior to that, I had an aluminum Soloist that I had been riding for OVER 10 years and the only reason I got a new road bike at the time was that I was offered an awesome deal on something that worked well as BOTH a road bike and TT bike (S5).

When the S5 and Soloist were stolen 2 years ago, I had a local builder make me a custom frame out of steel. I'll damned well ride that thing "forever".

When I was riding the 30 year old bike with nice wheels and tires on it (only possible because "standards" hadn't shifted significantly in that time frame) after the thefts of the Soloist and S5, it became completely clear to me that as long as new technology is compatible with the base frame, you can keep a frameset "alive" for quite a long time AND enjoy technology as it evolves.

When a "step change" is forced though, that's when things start getting limited. Here's a great example: On my current road bike, I'm running the SRAM Hydro R rim brakes. I've found that the hydraulic actuation really DOES keep the "lever feel" and modulation consistent over time.When the eTap hydro setups were announced, there was a conspicuous absence of a Hydro rim brake to go along with the wireless shifting and the updated hydro levers. When I asked the SRAM reps where they were, the response was basically "Rim brakes are old tech...why would we mate new tech with old tech?" And thus, the freezing out of some of the newer tech to the older standard has begun...and Shimano has gone "all in" on discs, and has never even offered a hydraulic rim brake with their newest groups :-/

Anyway, I think your "5 years at best" statement is overly cynical and misguided...but, I'm sure the bike industry loves that attitude in consumers!

I'd add that the risk of the current disc brake standard(s) changing is higher than the risk of the current rim brake standard changing.

Tom,
I'm with you to some extent. While I say that a bike won't be a forever bike, I should have clarified. Your next bike won't be your best bike forever. The next bike will be your best bike for 5 years, then you will buy a new best bike. Your current bike doesn't get sold, it just goes in the shed with all your other bikes.
Currently I have 12 bikes and it's growing. MY next bike will be a hydraulic disc road bike, then a hydraulic disc tri bike. Then I will have 14 bikes and be eyeing a bigger shed. One of my bikes is a 1974 Healing that I got from the original owner. He got given it by his parents to ride to University back in the day. Eventually it became covered in cobwebs and was about to be thrown out. The only thing that isn't original is the tires. Even the brake blocks are original. It has some very light surface rust. I'm restoring it and will have it as a museum bike/wall hanger.
A buddy of mine has a small bike collection. He focuses on quality more than I do. He has a 1902 something. He keeps it in pristine condition and rides it from time to time on flat group rides. Not bad for a 115 year old bike, with wooden pedals :-)
While my attitude may sound a bit cynical, I suspect if Dan did a survey, the average age of peoples best bike (or most recent bike) would be less than the 5 years I mentioned.

2x

What's the widest tire you will put on the bike?

Bigger than 30c go for the dick brakes, under that stick with rim-job.

There is no forever bike.....

Are you saying you can't get etap with hydraulic discs or am I missing something ? Note in the mtb I am yet to see a good way to convert the wheels to boost, a lot of mtb people not happy with that standard.

Are you saying you can't get etap with hydraulic discs or am I missing something ? Note in the mtb I am yet to see a good way to convert the wheels to boost, a lot of mtb people not happy with that standard.

I'm already riding them, thus my confusion. I just assumed they were available to everyone.

Yes, on a venge. For what it is worth I think the shimano system is better, unless you really don't like wires, which was the case with me.

No way 5-10 pounds came from disc brakes.

I bought 2015 Specialized Roubaix with disc brake... had a lot of fun with it, then I realized my bike is much heavier than all my cycling mates.... like by 5-10 pounds.

I switched to Specialized Tarmac with Durace rim brake, lost 10 pounds. So much faster on hill climbs now.

Unless you ride routinely in the rain, I can't recommend disc brakes (yet...until they get lighter). Just my personal opinion.

Agreed. The disc brake weight penalty is around .5-.75 pounds.

Feedback to the OP.
1. You can't currently get ETap with hydraulics.
2. Discs are more consistent and have better modulation than rim brakes. However, I agree rim brakes work great in the vast majority of road situations.
3. Carbon rims (especially clinchers) with rim brakes has never been a great setup. Discs and carbon rims makes a lot more sense to me.
4. If you're going to get discs, get thru-axles. Not a deal killer, but recommended.
5. Maintenance is more difficult with discs. Rotor clearance is tiny in discs. As a result, disc brakes can be a bit finicky to set up and very small amounts of runout in the rotor can result in mild rubbing. Also, bleeding brakes isn't hard but it does need to be done occasionally.
6. Flat mount seems to be the evolving standard but there are a hell of a lot of post mount bikes out there. Mountain bikes still primarily use post mount and SRAM doesn't even make flat mount calipers yet. I'd get flat mount if I had the choice on a new bike but you shouldn't have problems either way.
7. Forget about the idea of a "forever bike". You're always going to want a new bike. Get the bike you want right now.

I think you've gone the opposite direction on that...from what I've seen, it's more like .75 - 1 lb. at the system level in a true "apples to apples" comparison.

Feedback to the OP.

4. If you're going to get discs, get thru-axles. Not a deal killer, but recommended.

6. Flat mount seems to be the evolving standard but there are a hell of a lot of post mount bikes out there. Mountain bikes still primarily use post mount and SRAM doesn't even make flat mount calipers yet. I'd get flat mount if I had the choice on a new bike but you shouldn't have problems either way.
7. Forget about the idea of a "forever bike". You're always going to want a new bike. Get the bike you want right now.