The price of TVs continues to fall every year as new technology comes along. Unless this is the tariff question in disguise, I would say never buy a TV until you have to. It will be cheaper next year. IMHO
Should I buy another flat screen now while they are still relatively cheap?
My current Vizio 65" is either 7 or 8 years old, and it gets a lot of use. Is there an average life span on these? My previous Samsung 70" made it about ten years as I remember. I see that WalMart still has flat screens in that (or around that) size for relatively cheap.