I've been watching the price of salt cells creeping up, and probably should have bought a couple last year when they were in the $200 range. If I do somehow come across a good buy on one, I'd like to get a backup/replacement, but my current cell is only a year old. The last cell lasted well over 4 years. Do these things have a shelf life, or can it sit in my closet for 3 years without any degradation?