When to replace turntable belt?

+1 @mofimadness 

Wear depends on the belt’s material as higher end TT often use better belts 

Do we have to regularly measure the rpm variance? I bet the belt wear would be revealed by the rpm stability.

@mofimadness Well done.  @swong61 belts don’t all behave the same way.  You might be right for some.  Usually the belt will stretch and what mofimadness has outlined are things to listen for.  I will add that when the time comes it is not a subtle change, but more of a suddenly things don’t sound right kind of thing.

It can also depend on the belt material and where you live. E.g., if the belt is made of a rubber compound and you live in an area with low humidity, the belt will likely need to be replaced sooner, since the material can dry out. Information as provided by the distributor of my Acoustic Signature turntable, where the belt is supposed to last 5 years on average.

The good news is they are not expensive and can last a fairly long time...so if you're thinking it might need to be replaced, then replace it...