Thats why they put failsafes in them. The jbj for example can be set up such that one float switch activates the pump, a second float can act as an upper failsafe that will turn the pump off if the main float fails, and it will not let the pump run for longer than 3-30 minutes (based on user setting). Pretty much your only risk of failure is the relay contacts fusing, which takes 100,000 operations in the 95% confidence interval, and within that there is a 90% chance that when it does fail, it will fail in the off position. When I used to service swamp coolers, the average lifespan of a float valve was 3 years before it started leaking bad, and a saltwater environment is way harsher on moving parts than a humid environment. To each his own, but thats my 2 cents.