I don't think that you can destroy your Kindle by refreshing the screen too often. Many people have used their K1s for years and screens still work.
You are most likely to damage your Kindle while on the go, so don't let it leave the house without a cover. Or it may end up
scratched like this.
I also had couple of
Kindles fail after take-off in the airplane (I guess that pressure drop damaged something). But since then my family has done dozens of flights with several Kindles and nothing happened. Overall these cases seem quite rare. Also there seems little you can do to protect from it other than not take your Kindle to the airplane at all which kind of defeats the purpose.