Heating a bit doesn't "lead to drying of the electrolyte" unless it's already exposed to air. A properly sealed capacitor won't care about a moderate temperature rise. It can fail if pressure builds up, but that's outside the rated limits of the device.


The plastic sleeves I see are incredibly thin, and the cheaper plastic materials aren't very potent thermal insulators. Where did you get this information?

I'm using some electrolytic capacitors which are wrapped in almost 2 mm of paper (pretty good thermal insulator). They are still functional after 60 years of service.