A discourse on electrolytic caps can be found here.
My recommendation for preservation of such artifacts, so far as the electrolytic caps therein are concerned, would be to store them in a cool, dry place, and use them one in a while.
Dry-out of the electrolyte solution is a phenomenon that follows an Arrhenius relationship, which predicts roughly a doubling of process rate for every 10°C increase in temperature. Hence, keeping things cool and dry helps. The dielectric in such caps is formed electrochemically, and when unused for extended periods, 'lytics can self-cannibalize to a degree. Using them periodically helps to minimize this effect by engaging their self-healing mechanism, and limits the possibility that the dielectric will weaken to a point that failure will occur when an item is next put into service.
In short, treat your vintage electronics like something you care about and want to preserve, and enjoy them in the process.