The same Windows kernel driver can work from NT 3.51, released in 1995, to at least Windows XP, and for many classes of drivers Vista and Windows 7. During that time the Windows kernel has undergone numerous fundamental improvements (plug and play, power management, etc), and yet the core kernel _concepts_ have been kept stable. Can you point me to a Linux distribution that maintains a kernel for 15 years?
The frequency of kernel releases would be immaterial if the API was stable or the changes formally tracked and documented. The latter is actually preferable because it wouldn't stop the innovation.
Oh, yes, the commercial distributions are trying to maintain a stable kernel for some time (although far from 15 years) - of course they would; this is what the vast majority of businesses and users really want and need regardless of what the stupid document "stable_api_nonsense.txt" says. Alas, it is actually causing further incompatibilities and problems between distributions - everybody has a different version, with different patches, etc. It is a nightmare.
Sometimes I cynically suspect that this is on purpose, or otherwise expensive support contracts wouldn't be that necessary.