Thanks a lot, that's great info! Do you happen to know if all current models from the three manufacturers you mention can use folders, or if there are exceptions among them?
As for adapting to the status quo - yes, I guess I will inevitably have to, at some point. Still, I'd like to delay the inevitable for as long as I can.
I really, really like my folders and I even briefly considered buying a stack of old PRS-505s (they can be found on eBay, sold in stacks of 10s and 20s) in order to avoid the problem altogether. Until I remembered that Li-Ion batteries begin to decay as soon as they're manufactured, which scuppered that particular bright idea. Had that not been the case I would have gone ahead, since I have no real need of any of the bells and whistles of the newer readers, only a good screen and decent functionality.