Abs light comes after riding a mile or so want go off

Light on is no indication of wear on brakes. Volvo has lots of issues with this. If you have a speed sensor code for the right rear wheel speed sensor that keeps coming on, then you need a computer. 35 years working on Volvo's professionally 98-99% of the time it is the control module-check codes first though

You should have a shop read the error code to be sure, but failures of the ABS computer are common on these cars. We pulled the ABS out of our 98 S70 and sent it to a shop in LA that rebuilds them. I don't have the shop name here but we found it on the Internet, I remember only that the shop owner has a Hispanic name.
Turnaround was quick. We put the ABS computer back in and it has worked just fine since then (3 years).

You have an
ABS fault tripping the light. GET IT SCANNED.
NOTE: autozone wont be able to access the ABS computer.

You have wheel sensors on all four wheel assemblies,if the light is comming on have your brakes ckecked.