That came to mind for extending device support. As I understand it though the hardware drivers are all closed source and end support rather quickly. I believe that the drivers are sometimes the source of the problem which sort of complicates extending the lifespan.
The only problems I experienced are when the wireless bands are deprecated. I'd still be rolling my n900, otherwise. Old drivers or not, there is/was still some development going on; Leste & PostmarketOS, IIRC.