Wowza, respect for taking on the ADK grid. As a Vermonter I have an idea of what you’re in for; I remember when Sue Johnston did the same in the Whites a couple years ago and was soundly impressed. In the Adirondacks, you get even longer approaches! Lucky you.
I don’t want to spray but thought I’d comment on some aspects that I have experience with…so, if you know this already, forgive me for spraying.
I’d be very skeptical that you could gain fitness throughout the year as a result of the repetitive, high-volume mountain travel you’re taking on. Even maintaining your initial fitness level will, I imagine, be difficult throughout the year. Unless you are supremely fit on Jan. 1, it might be smart and proactive to plan for a slow fitness decline throughout the year. And by supremely fit, I mean Sue Johnston-level fitness (Hardrock 100 winner, women’s Barkley Marathons record, etc). This is especially true given that you will be starting in winter conditions, which can be super taxing as you well know. The first month, if you do a long winter outing every 2-3 days on average, could be a massive shock to your system that could be particularly tough to recover from (5k’-8k’ per day is nothing to shake a finger at…same for 10-15 hour days). However, I assume you’ll be basing yourself from home for most of your outings, which will make recovery easier. Take what I said above with a grain of salt since my long-duration mountain trips have only been in the backcountry, and recovery was really not part of my trips until they were done.
One upshot is that you will likely get a reprieve from time volume once the snow melts since travel will become a bit more efficient.
As far as preparation goes, you would probably be happy during your grid year if you devoted training time beforehand to zone3+ workouts to increase your economy. You’d be getting more bang for your buck since “tuning” yourself up like this would mean more efficient travel for less energy. A big base is great but your fitness would be even better with some high-end work thrown into the mix. Your climbing legs would probably thank you too if you committed to a general strength-> max strength-> muscular endurance component of your training plan centered around climbing efficiency. As far as strength training during the grid year, I can’t really comment on the effectiveness of that; maybe if you have extra energy? I used these tenets to train for a month-long bikepacking/hiking trip in the Colorado 14ers this past summer and was happy that I did.
A cautionary tale based in personal experience to end. The aforementioned bike/hike trip I did was, like your grid plan, a big step up in commitment and intensity compared to anything I’d done before. Despite 6 months of really solid training (ending up being much fitter than ever before), I got completely and totally wrecked. Granted, I was sleeping in a tarp and my diet was frightening, so my recovery during the trip was almost non-existent. However, I got served an entire counter filled with humble pie by the time I ended my trip; I had thought I had the fitness to take this on in a healthy manner, but was naively mistaken. That trip finished in late August and I’m currently still recovering from Overtraining Syndrome as a result. I wouldn’t change anything I did since it was a priceless educational experience (the School of Hard Knocks is deadly effective) as well as a quality adventure; as such, I feel qualified to share personal experience relating to planning big, mountain-endurance related trips. I don’t know your endurance background but it sounds very accomplished and solid. I hope all this doesn’t come across as assuming you don’t know what you’re in for. That said, OTS is really something to consider when planning your grid year. My trip lasted a month and I’ve been dealing with it for almost four months; imagine what a whole year might do to your system. Is that something you’re willing to take on to complete the grid? I know this is a bummer of a topic to bring up, but when planning such an extreme trip I strongly feel that potential OTS should be as important a consideration as planning and executing your training.
That said, I will be rooting for you across the Lake with high hopes for your success. I can’t imagine a better method than a calendar year grid to get to know a place intimately.