Kobo is indeed great. In addition to continuing to support seriously old models with firmware updates, they’re relatively friendly toward hacking Kobo devices to run third-party reading software like KOReader. (While they don’t officially support doing this… unlike Amazon, they don’t take steps to prevent it.)
For the long-term support, it probably helps that the devices run Kobo’s own Linux-based OS and not Android (something of a rarity these days). But it also takes a committed manufacturer to keep supporting older devices. According to this fan site, the original Kobo Touch model from 2011 got last month’s firmware update.
