Also, like Jonas Grumby
says, "Inner Light" looks and smells like a memory implant. Picard remembers the decades, but did he live through them? Or did ironweaver Kamin? For the first few days of the memory, Picard behaves like Picard - but for the following decades, we don't necessarily see him making any decisions in life, taking any action, thinking any thoughts - it could
just Kamin doing the living, the thinking, the choosing.
"Inner Light" is ambiguous there, though. Would Kamin have had the skill or the drive to study climate change or solar behavior? "Hard Time" does not present us with such practical handles to the problematique. O'Brien spends twenty years in hell, yeah. But does he make any choices there? Had he really been locked in with that other fella for twenty years, would he have made any of the choices the memory-implant version of him is seen making? It's all awfully generic, rather than something specific either to a hero-in-a-jam like Picard or even to a "borrowed" or completely fictional personality like Kamin.
Memory implants could well be argued to fade in a day or two, if not sooner. Neither Picard nor O'Brien would have had their brains undergo any actual learning activity or major cognitive processing of any sort... Did Picard even learn to play the tin pipe - or was Kamin's lack
of skill part of the dream, and his actual learning at the end of the episode a triviality (like tin pipe playing probably would be to many)? Remember how the characters in the dream actually go out of their way to say that Kamin doesn't know how to play...