I use my R-29 in a fresh water lake in the summer and out on the ocean in the winter. I also do not plug into shore power. I have solar also.
Your zincs will last longer in fresh water. It is still a good idea to keep a eye on them. You can still run into problems if you are in a marina and you are next to a hot boat or on a hot dock. So it is good to keep a real close eye on them for the first few months.
My zincs last all summer long in the lake. I change them when they get to 50%. That is when I haul my boat out to the ocean for the winter. With that being said it is important to note that I do not store my boat in salt water. When we are done cursing i take her out on the trailer and flush out with fresh water, inspect all zincs,shaft and prop. Then put my full custom sunbrella cover on her that has clear panels that are over the solar panels so batteries stay full, and put her in dry storage.
I do not have bottom paint at this point. There is no reason to have it the way we use it. once a month I will bring her home from the lake and power wash the bottom and do whatever maintenance i feel I need to do. There is not any real bottom growth at this point but I just like to stay after it before it has a chance to build up.
When we are on the ocean I am never in for more then a month and it is not a issue. We are moving alot so it never has a chance to build up. Nothing worse for a boat then to sit. We have over 300hrs on our boat that we have had for just over a year.
I also put at least three coats of 3M wax on her a year. Yes that is done even know I cover her when she is out of the water. It is very easy to do while it is out of the water. My boat will still look new after many years down the road.
The trick is to wax her before you ever think she needs it.
Well that is more then you asked for ,but hope it helps.
Stuart R-29 Spirit of Gratitude