So something that has come up a lot is Fallout 4's use of fusion cores. One thing that seems to be thrown around is the length of time post T51 models were supposed to have lasted with their internal energy source. I've seen 100, 200, even 500 years being mentioned. So which is it? I admittedly have not played much of the earlier Fallouts so I'm not well versed on their specifics but from what I've read, the T45 had something similar to Fallout 4's fusion cores and after that there was an internal long term energy source. But was it ever stated what that expected experiation was? If it's 200 years, then it makes sense why they'd have to revert back to using the throwaway fusion cores since it has been over 200 years since the Great War. I'd just like to know what was actually meant to have been 'lore correct' for the PA power sources

That's certainly a possible explanation.

Another possible explanation is the fusion cores ARE the internal generators but they've decayed to nothing and each only has a few days of operation left.

Fallout 1 and 2 both say that the power armor's battery lasts 100 years,

but given that Fallout 2 takes place 160+ years after the war, and PA still works, they apparently just started [censored]ting at that point.

Ahh ok. I know it's probably silly to use the Fallout Wiki as a source of reliable info but it was the same as you said, I just didn't want to use that as a source. I've recently seen people lashing out at the fusion core idea as 'not lore friendly' due to the internal power source. But I could have sworn it seemed like those would have run out by now. Good to see someone more or less confirm that the internal power is likely depleted. At least then, even if someone doesn't like the mechanic of fusion cores, it does seem to still be plausibly lore friendly

Eh, the BoS would probably have found a workaround.

They did. It was called not authorizing Power Armor to anyone below the rank of Paladin.

And using an auxillery power source like fusion cores

I actually don't mind the retcon to Power Armor's power supply. Besides, it's not as though Fusion Cores are rare. I could easily just rock my armor 24/7 at this point. I'm sitting on 50 cores.