They used to say around 1000 times for CDRWs. I have some HP 4x CDRW's still working fine for around 10 years. I dont use them much now but some of these must have been used around 300 times - used them a lot until I got my first USB2 external HDD.
If any give trouble for erasing use the freeware Superblank - gives new life to bad CDRW disks.
Lots of times .. infact in some cases more than the manufacturer quotes ... so u can't reallly fix a particular no. of usage ... over 500 time i guess (mine is doing over 200 times) ...