Overall the upgrade to the Paperwhite is comparatively fairly new (around November last year), after working with one of the early touch's for half a dozen years starting back in the early 2010's, then another touch (can't remember precise model) after it was broken down to the point the power button wasn't working at all (not too relevant, just background).

Paperwhite upgrade was mainly because I'd been stuck on tiny storage for a decade or so at that point, and I'm mainly working on more fan based stuff rather than stuff from the cloud, so I can't easily redownload stuff onto the kindle directly, and thus storage was a serious issue towards the end.

On the paperwhite I still have 7k mobifiles, and it seems to be causing serious slowdowns and power issues (the kindle likes warning me when I put a bunch of new files on that it will lead to reduced battery life, which does seem to be true) and sometimes the internal search struggles to find certain files that I know are on there (I can be reading something in the morning, and then when I go back in the evening it can't find the file, but it can find something else I couldn't access that morning).

Any advice on trying to minimise this would be greatly appreciated, and if people need more information to help then let me know.