I think consoles have two lifespans:
a) Up to the point it loses relevance in the mass market
b) End of Life set by manufacturer
The Neo Geo's lifespan was 14 years since it was EoL'd in 2004, however I think by this time it had already lost its arcade mass market appeal when the last of bevvy of small arcades were dying off in the late 90's along with consoles such as the Dreamcast acquiring some SNK titles on its platform.
The PS2 was EoL'd in 2013, mainly because it probably still had a very strong running in the South Americas, Arfricas, and some European countries but i'd say at least for the primary market, the PS2 died in 2008-2009 with its last hurrah of games being Persona 4 and such. PS3 was still pretty meh at the time.
for something like NG
EV or WaterMelon Co. , i'd consider it a fan revival. Video games/consoles can only die physically and when a person stops caring about it, so it's a person-by-person basis whether this revival is true. If I were more into Dreamcast and had a full collection and had some new NG
EV relases, i'd be pretty psyched to break out the 'ol girl and play some new games. I certainly think its cool if you're a developer to go back and as a programming challenge, program a game on legacy hardware as a personal test of abilities but with certain types of these companies, it feels more of a cash-grab. I know there's a lot of work involved but it really depends on the company. I'd be more inclined to buy something from WaterMelon than NG
EV at this point, since their games feel more like a genuine ode or swansong to their console of choice.