halocline
Contributor
Skills are the same once you have them.
I don't think this is accurate. Cave diving successfully depends on building and maintaining specific skills and habits, and these things take regular practice. It is possible to practice most of these skills, like precise buoyancy control, line work, gear related problem solving, in OW or even a pool, and reviewing knowledge is easy to do anywhere. But you're not going to take a cave course, learn a bunch of new things, go a year without practicing, and then be able to simply pick up where you left off. At least I couldn't do that and I've never met anyone who could.
But, answering the the OP's question, most of the people I cave dive with live several hours away by flight from the caves, including myself. If you really want to do something, you find a way. I can only afford to do 3 trips per year to Mexico (where I dive, usually 10-14 dives each trip) and I've found that this amount of frequency allows me to pretty well maintain my skills at the level I dive at and feel pretty comfortable. It might have helped me that I had over 1000 OW dives and DM experience before starting cave courses.
But there are many people who learn to cave dive and then don't continue because they are not able to maintain their skills and 'cave confidence' through regular practice.