Are they ceramic or steel? Steel bearings are softer and lose shape after time. Won’t hurt to replace.
**edit not saying to take apart the bearing cartridge***

If they spin smooth and there is no play then there is no need to replace. If you haven't been riding in complete downpours on a regular basis they will last a long time. Bearings today are sealed well so no worries.

DON'T MESS WITH IT! Especially if you have a Speed Concept. I'd not worry about it until 10 years or 100,000 miles, or unless you start to have trouble with it.

When you get to the point that there is a problem, replace the bottom bracket, not just the bearings.

Thanks for the advice. No noticeable issues at all. There is no reason to change.

I'm not sure if they are ceramic or steel. I would have to look that up. The general consensus seems to be if is ain't broke, don't fix it. Nothing leads me to believe there are any problems with the bottom bracket. Neither while riding nor inspection on the bike stand.

No worries there...I'm a fair weather rider. If it's raining, I'm on the trainer

Keep in mind that the SC uses the Trek BB90 standard and the BB is really just two cartridge bearings set directly into pockets milled into the carbon frame. Depending on which crankset you are using, there are diffferent bearing and bearing covers used.

Personally, I'd regularly disassemble, clean the bearing pockets in the frame and grease the pockets and spindle cover overlap with a tacky type grease to keep out moisture and road grit. This would be more important if you ride and race in wet conditions or live somewhere where the roads are sanded in the winter. Probably less of a concern for dry conditions-only riding. OTOH the BB90 setup is really easy to pull apart and reassemble. And cartridge bearings may be the cheapest part on the bike:) Download the SC maintenance manual to get a look at the BB90 configuration.

What you want to guard against is wearing the BB90 bearing pockets. Trek doesn't really speak to what causes these to go out of spec. I only speculate on the wear from contamination or perhaps spinnning a failing bearing at times. But the fact is that Trek sells BB90 bearings that have 0.1mm larger OD to be used for "loose" BB90 bearing frame bearing pockets. If the wear is too much for the special bearings to compensate for then they require the frame be sent back to Wisconsin for repairing the bearing pockets. There are SC owners here on ST that have had to go thru the process. I also have a friend that had to do this for his Trek (we have plenty of wet conditions and grit covered roads!).

The momentum of the crank can mask bad bearings.
Take the crank out and spin each bearing by hand, put some side load on it while you spin it.
If still smooth. put it back together with a little fresh grease on the spindle.

I'm looking to swap out the SRAM components that came with my 2018 SC and put in Ultegra 6800 so that I can bring my powermeter over. Can I just slide an Ultegra in after taking out the SRAM Quarq Power Ready crankset?

pretty sure that isn't going to work with SC being BB90

no, the SRAM BB has a 22mm ID on the NDS, the Shimano needs 24mm.
At the minimum you need to change that bearing

As David mentions above, you'll need to swap your 22mm ID NDS bearing for a 24mm ID NDS bearing. You will also not need the DS wave washer and NDS metal bearing cover, but you'll need a 24mm NDS bearing seal/cover. Trek offers a full kit or you can get parts online at RWC/Enduro or Wheels Manufacturing.

Trek offers all the specifics here: https://trek.scene7.com/...t_Service_Manual.pdf

Going the parts way...

One 24mm ID NDS bearing: $12.99 (ABEC 5 version)
One 24mm ID NDS outer seal: $2.50

and everything else that's currently there stays in place? 22mm stuffs on the driveside?

Or $40 for the full kit.

Yes, that should work. The GXP DS wave washer won't be necessary as bearing preload will be set using the Shimano NDS spindle end cap. You need a Shimano preload knob cap tool if you don't have one already.

22mm has to go otherwise the Shimano crank won't fit. For what it's worth, you don't need a Shimano crank to work with a Shimano FD/RD. The tooth spacing is the same for both Shimano and SRAM chainrings (and, IMO, the new Shimano 8000 chainrings aren't that great). My $0.02, I prefer the GXP standard. It does a better job of distributing stress from the DS to the NDS bearing.

My problem is that I'm running Ultegra Stages and penny-pinching. I'd love to find lots of dollars in my couch and just get the Quarq since the crank is ready for it.