In product reliability study there's a thing called a 'bath tub' curve, shaped a bit like, er, a bathtub It has probability of failure on the vertical axis and time on t'other.
What this means, broadly speaking is that when something is new it's likelyhood of failure is relatively high. When it settles in it generally gets more reliable and when it reaches it's planned obsolescence it again becomes more and more unreliable as time progresses.
Of course some gear is 'badly designed' and lasts forever, which is no good for the manufacturer if they run out of customers.
My Little Mark II was an immediate failure as an example although I appreciate that Mark Bass failure is rare.