This my 3rd full winter since getting "hooked" on fishing ... Here is my "winter list" ...
1 - Learn more - Catch up on reading, fishing shows. I record them and collect the magazines during the season. I read them when I travel for work and over the winter. I also buy at least 1 book to learn more.
2 - This site ... nuf said there.
3 - Fishing related hobbies. - I LOVE making jigs from scratch. Pour, paint, skirt. I also make spinnerbaits, buzzbaits, swim jigs and chatterbaits. I mess around with small batches when I feel like it at night OR on the weekend.
4 - Organize tackle. Like my entire tacklebag from scratch.
5 - NEW - Learning to tie bucktail jigs. Just because.
Honestly ... this covers me for a lot of "down time" NOT fishing. It does not replace it but I found joy/satisfaction in doing this stuff and even more pleasure in catching with the stuff.
Good luck! I truly feel your pain!!!