Do the research. Yes I too ended up adding to much salt to my pool because I got a bad reading on dispaly. But realy DA I should have noticed from past experience I was adding way too much salt to bring the level up. However, the additional salt does not ruin the unit it was bad prior to that. My resaerch reveled that I shold expect 3-5 years of use from the unit based on hours run, I should get about 10,000 hrs out of the unit(of course there are some variables,common sense tells you this). Here's my finding from PoolCenter.com, "What happens if I add too much salt?
Over-salting will not harm your chlorine generating system, but will lead to a salty tasting water. For some, this is not undesirable as it will more closely match our bodies natural salinity level, making it more comfortable to swim in. If it is too excessive (over 6000 ppm), you can sustain corrosion damage to metallic equipment such as stainless steel handrails, ladders and filters, light rings, or copper heat exchangers. To reduce the salt level, dilution is the solution. Drain some water and refill with fresh water."
JUST do the research is my suggestion