I had similar problems on my wooden boat, compounded by the fact water not only got into the cable joints, but also into the deckhead.
When I cut out the sponge and graved in new wood I was determined not to replace the glands but get something better:

The KISS rule applies. As well as an added bit of ventilation it means I can have an uninterrupted run of cable from masthead to the instrument panel and VHF. The next time the mast is stepped I just pull the cables through.