Like CD-RW, it varies.... I've had CD-RW media that managed precisely ZERO uses.
If the drive and media agree well with each other, you can get many uses - I believe CD-RW is supposed to be good for 1000, probably similar for DVD +/-RW, but it's a LOT more variable than the performance of write-once media.
And in general, best NOT to rely on rewriteable - ok for testing, but that's about all!