How long can you keep having nail extensions done for?

I've recently had gel nail extensions and have had them refilled once... how long can i keep doing this for? indefinitely? can you keep on just getting them refilled or should you start again at some point? and should i get them all removed ever?How long can you keep having nail extensions done for?
I've been having my nails done for about three years now and I've never had them all done again at one time. They get done again as and when I break them. Going today and need a new one doing on my thumb, broke it yesterday!How long can you keep having nail extensions done for?
I am just coming up to 6 years with constant acrylic nail extensions.


My own nails are a bit brittle underneath but they were never good anyway.
I guess as long as you can afford to keep up the maintenance!