Wax-potting is a procedure to preserve the coil of a pickup and avoid feedback, but not only that!
Wax-potting is also a fine tool to determine, to what degree the bass-guitar pickup is micro-phonic.
Literally: the portion of the sound of the instrument which is picked up by means of a 'microphone', i.e. the pickup.
Most the time a micro-phonic pickup is not what you want, but a little bit of the vibrations of the bass ads a nice
acoustic accent to the sound. So it's not all bad!
Talking about wax-potting, brings up the issue of drying of the wax and what that does to the sound. The first 3 weeks, after the pickup is wax potted, it takes to let the wax dry so the core of the coil is dry and the real sound of the pickup starts to reveal itself.
Now there is another 5 to 6 month required to let the sound get to its maximum.
Now we are talking about the crystal structure of the insulated copper wire.
During the winding process, the crystal structure of the copper is stressed and the purity of the copper is less than before.
Strange enough, most of the crystal structure recovers itself within the next 5 to 6 month. The aging process does nice things to the sound. The sound of the bass-guitar will improve, due to the pickup yielding more upper harmonics and the dynamic range expands during that period of time. The changes will be subtle, but audible for trained ears.
We are not talking 'voodoo' here, but real experience of myself and various musicians who noticed this phenomena.
The following 20 years even more subtle changes can be observed in the sound, fortunate musicians who own a vintage instrument can vow for that.