Thanks for your responses so far. I have a 685 and was looking around for a used N803. Since they came in 1999, i was curious if they hold SQ even after 14yrs. They still sell for 1/2 the original price so they must be good.
It seems the speaker placement(near heat) and other factors mater.
I guess speakers do fine but its the subwoofers that would have a shorter life due to excessive vibrations/cone movement/proximity to floor.
Would be nice if people can share what older B&W they have and how since how long.