How can I evaluate a potentiometer susceptibility to change?
Don't worry about it. If trimpots shifted around a few percent with minor vibration they'd never be used. Just about any trimpot from a reputable maker (and quite a few from disreputable ones) will be fine. 

Minimize the range of the pot (don't require it to be set to 0.1%) and try to use it as a voltage divider rather than a rheostat. If you must use it as a rheostat, keep the setting away from the very ends of the range and try to use a relatively high value (avoid 10 ohm cermet for example, if you can) so that CRV (contact resistance variation) is not much of a factor. 

But a few percent stability is not a high bar.