I keep mine mounted year round for 1.5yr now. I ride both in the day and night, so I am too lazy to take it off. It seems to hang on tight even on car trips. But I did notice the o-ring that mounts the light has lost some strength and elasticity. Most likely due to heat and UV. I would probably replace it soon...not because it might break and fall on the freeway, but its not keeping the light pointed in the right direction after a big bump.
I think with clamp type mounts like the gloworm, you probably wont have that problem.