David,
Nearly 100% of my experience using AA NiMH batteries comes from using the Pentax DSLRs in the 2004-2009 time period. I had the best NiMH batteries I could find... at the end, the Sanyo Eneloop, now with other brands carrying them... and the best charger I could find ... La Crosse Technology BC-900... Still have both of them, the charger is still great, the Eneloops are still working 13 years on. I use them in a host of other devices. The Eneloops finally solved the storage problem and maintenance problems of NiMH batteries, in my opinion. In that time, Li-Ion technology batteries, even in AA format, were much more expensive and the benefits of using them questionable. (Actually, the best performance I ever got out of those cameras was with the one-use AA Li cells ... One set of them once lasted me through a four week, 2600 exposure trip.)
However, the first Pentax which had a dedicated, custom form-factor Li-Ion battery (can't remember the name) outperformed on battery life all four of the previous Pentax cameras. The standard BLM-1 in the original Olympus E-1 outlasted the Eneloops in an adapter by a factor of three on a charge. That experience colors my view of this stuff.
That said, I don't disagree with the notion that battery availability will be the death of many an old digital camera. As will parts and service availability, which applies equally to film and digital cameras, and the battery issue can as well affect film cameras. It's why I prefer old mechanical film cameras with no meters, and generally when I move on from a particular digital camera, I don't go back. I loved my old L1, would never buy another now; same for the 2003 E-1 which is delightfully still working as new and the BLM-5s still available easily. Battery life will sound the death knell of my very entertaining and useful Light L16 (non-replaceable battery) just like the availability of a current OS upgrade and apps compatible with modern systems and needs will eventually murder my mid-2012 Mac mini.
As much as these things are lovely, I can't see going back to them over the equally wonderful and better performing current offerings for which batteries, parts, and service are easily available. They are devices, locked into their time, just like my 1967 Lancia Fulvia Coupe is, and it takes a lot of effort and energy to keep them going and usable. You only do that kind of thing because you like them ... the very meaning of amateur involvement in a hobby. Not because it makes any sense.
I can't see much point to complaining about the effort and trials it takes with old cameras, or with old cars, or with old computers, since I know in all ways I can buy a modern, up to date replacement that will outperform them in every particular. And that I even like just as much. I just enjoy the old junk, and find the tribulations of ownership/use part of the charm of messing about with them. 🙂
G