still can use for 5-10 years, but it's low efficient, will burn more gas. so I decided to change to high efficient. Best time to buy is spring time from March to May while those company is not very busy.Normally they have promotion until May,30th.I bought the high efficient (92%) two stage. but not variable speed. ( that will cost more than $4100). My price is $3450 include tax.So far I think it's the best thing I did for the house.The bill is really going down.Hope this helps.