although i agree with your point somewhat, i think there's more to this whole topic.
you kinda have to define what 'lose their hunger' means. it means something different to everyone. personally, i think that usually someone that drops a hot debut is naturally going to get a lot of respect and admiration because it is unlike anything we've heard before. as soon as they drop their second album, people are quick to criticize and quick to say an mc has 'lost his hunger.' snoop is a perfect example. i think that if 'tha doggfather was dropped as his debut, rather than 'doggystyle', we'd look at each album in a different light. much the same as with tha dogg pound.
some mc's definately 'lose their hunger', but who knows, it could be that they're bored themselves and want to try something different. you can come at this from almost any angle - when you get paid to do your hobby, you look at it as a job. as soon as people expect things from you, you get sick of it. maybe they're sick of the expectations and just don't have the hunger any more because it's not something to strive towards anyway.
in any case, i think we're all a bit too quick to judge when it comes to a new album by a 'legend.' all you people that thought the 213 album was pure garbage, i want to ask, what the hell were you expecting? i have no doubt that it's classic 213 material. i didn't expect a shred more than them and was actually very pleased with what they came with. it's a album consistent with their personalities and i think it came out damn near perfect.
i see debut artists as new girlfriends. they're real dope when you first meet them, but after a while when you're more used to them, you can see past the infatuation and finally realize that they're just human and they do have imperfections.
so as for your question, i agree with you in the sense that, yeah, mc's can lose their hunger, but we also lose our fresh ears when we expect something from someone. it's a double-edged sword.
THIS IS MY OPINION SO DON'T GET YOUR PANTIES IN A BUNCH