Toyota Repair: 2000 Toyota Camry starter

Question
Hi,
Maybe once a month when I start the car, the starter makes that awful slipping/stripping/whatever-it-is noise. I stop and turn the key back and try again.  It starts right up then.  This has gone on about a year.  Of course I know I need to have the starter or a switch in it replaced.  My question is to know if it is likely for it to suddenly give up the ghost or will it continue as is and gradually get worse until it doesn't work at all.  
Art

Answer
The problem is the flywheel, some of the teeth are stripped or damaged, if the engine happens to stop there after turning it off you will get this noise caused by the starter gear not engaging, the ring gear of the flywheel can be inspected by removing the starter and slowly rotating the engine by hand, reolace the starter and the flywheel at the same time.