I will try to check a few things you mentioned

Well, me and my hu*****and both drove it when we needed. I myself seldomly use the air conditioning, since :) I am very slim, :) normally deal ok with the hot weather. so, it's hard to recall now if it took place "suddenly" or "gradually" without our notice.

Ok, where I can find the place to take a check on the level of the refrigrant?

Thanks!