So, there are these zinc anodes that protect the metal underwater from getting eaten up.
At Port of Sidney out on G-dock, we went 12 or more months between changing our zincs.
Here are what the zincs look like when new:
Here are our zincs after 3 months at Fisherman's Wharf:
The split in half zinc (it is supposed to be split, it is a cuff style) is only 4 months old. This is normal for a lot of people and a lot of boats but our boat is very electrical neutral (or at least has been so in the past) and we have had great luck with low galvanic corrosion. Our zincs get eaten enough that we know they are working but not so quickly that we are afraid for our boat.
I'm glad we are leaving here in a few weeks. At least I know that our fresh zincs won't be consumed before we leave and the nice thing about anchoring is less stray current to worry about.