Some of the other posts touch on the topic of the pros and cons of switching cassettes, and I wanted to expand on it.
The big pro of course is convenience, you can just pull out your disk, put it on your bike and off you go.
The big con is chain/cassette wear. Chains and cassettes wear together. If you let your chain go too long, it will “stretch”. The cassette will wear in order to match the chain and the combo will work together fine, until the chain breaks. If you were to put a new chain on at this point, it wouldn’t match your worn cassette you would most likely have shifting problems. That being said, if you take care of your chain, keeping it well lubed and such, and replace it before it gets too worn, your cassettes will last a long time, and you could switch them without problems.
Another thing to think about is how much each cassette is being used. If you put a “race” cassette on your disk, and only use it for a half dozen sprint and olympic races during the year. It’s not going to wear as fast as your other casette and chain that you are piling the training miles on. Again, if you keep the chain lubed and replace it often, at least yearly depending on your miles, that just means your ‘race’ cassette will look great and last longer.
One more thing to consider is what cassette are you going to put on your disk. I assume you are going to use the disk for flat to rolling courses and not epic hilly races. So you might want to think about putting a 11-21 (650c bike) on it, or at least some other cassette than what you normally use. Knowing how to change cassettes, and having the tools, and spare cassettes, will allow you to change it depending on the course and how you feel. I switch between an 11-21, 11-23 and 12-23 all the time.
So, after this lengthy post, my recomendation is to get another cassette, possibly a different gear combination than what you have. Get the cassette lockring tool and chain whip to change them, and go to your LBS and have them teach you how to do it. Practice it a bunch of times and you will be ready for anything.