I have an irritating leak at the mast which means that I have to switch on
the automatic bilge pump about 4 times a year.

If your pump turns on 4 times a year, you have more water coming in than I do.
If I waited for the switch to be tripped, it would probably never happen. It
seems to stay at about an inch or so, unless I pump it dry...which lasts about
a week and then it slowly goes to about one inch and oddly stays there.
Fix your leaks!

RB