The longevity of a rewriter is not as high as that of a CD/DVD-ROM type drive - that's why I always recommend that a rewriter is used for the sole task of burning.
Manufacturers, even those that rebadge other makles' products, usually indicate the anticipated minimum life span of their drives.
But there's no average - one drive might last 18 months, another two years and a third pack up in the first year.
My first CD-RW drive was a TDK Velox 12x10x24 (actually a rebadged Plextor, one of the best makes around), which packed up within four months despite minimal use.
TDK replaced it and that auffered exactly the same problem after a few weeks; the replacement for the second proved to be a TDK CyClone with 24x write speed as the Velox had been discontinued.
Price of the orignal rewriter was £68 - the then new CyClone was £189 at dabs...:-) TDK didn't make any money (the two earlier ones went back to its Luxembourg HQ and back at TDK's expense), but the customer service was fantastic.
Thankfully the CyClone is still doing sterling service.