After trying many pickups including inside mics(too much feedback) I settled for a brand called HOTWIRES which is two stick on pizeo pickups, forget the glue that comes with them and use bluetack. Place one pickup behind the lower (physically not musically) end (D string)of the bridge and one in front of the high(G string) end of the bridge. As my Fender Leo banjo was used in a highly active (we tended to jump around a lot) amplified folk group I did not hesitate to drill out a hole and fit a 1/4 inch jack socket, it did not seem to make any difference to the ring or unamplified sound
. I have no idea why your bacus berry deteriorates over the nite
There was an earlier thread about mutes, I used a metal mute from time to time. on my amplified banjo, it produces a harp like sound and makes the notes sustain (ring on) MUCH longer. Try working out a two strings played together version of Si Beg Si More or Planxty Irwin You can get a 5 string banjo folk solo that will bring the house down.
Regards Ted