That's sort of the issue the OpenMoko faced. It was designed to be a device with long-lasting support - but support died quickly because so few people had one.
TBH community distros were pretty long lived (and let's be honest, those were the only ones that mattered). At least SHR was actively maintained to around 2012, with last generated image being from April 2013, and I seem to remember QtMoko being maintained even tad longer. IMO that wasn't bad for a device released in 2008, especially for today's standards.