In modern, medium- to high-end equipment, chances of dry solder joints are slim to none, especially in radio equipment, where your solder process needs to be especially safe against this kind of failure to not inadvertedly add parasitic capacitance.
I'd agree, electrolyte capacitors are a prime aging suspect. They've gotten better, so in most cases, I wouldn't even expect a capacitor failure after 20 years from a device with medium density (i.e. enough room for mechanically large caps) that came out in the 2000s.
What's typically not good after 20 years are batteries, which are still common to preserve volatile memory (e.g. channel settings) and by more more commonly to keep an internal timekeeper running.
Some thermal greases (between electronic components and coolers) tend to deterioriate over time.
Dust and dirt are actually most likely to pose problems due to clogging cooling structures. So, a dustproof plastic bag might be a good idea. Make sure it's not 100% airtight, though, if the device is exposed to some thermal cycling: you don't want moisture to condense within the bag.