My KreepyKrawly lives in the pool. Even when I'm swimming, I just tuck it and the vacuum hose behind the pool ladder.
Only time it comes out is when we have guests over. Makes things much easier.
The extra time in the water is probably degrading the plastic a bit faster, but nothing really noticeable. It will probably look "bleached out" a bit faster as well since its always in the sun, but again, nothing I'm worried about.