Right now, I’m alternating between hunting two horses. I ride the super reliable one on days I know I will be asked to volunteer as a whip (typically our weekday hunts) and ride the greener horse on days when I can hang at the back of whichever field is appropriate for him at a particular fixture.
I also do a “making it work” version. Typically, the winter schedule for my horses involves 1 day hunting, 2 days walk/trot hacks around the pasture if evening or early morning or on gravel roads if during the day (would love to do more canter work at home, but footing often prevents this as I have no arena and don’t want to tear up the pasture) and 1 jumping or dressage lesson. If I end up hunting the same horse 2x in one week, especially if I whip in twice on the same horse within a week, I either don’t ride other than the hunts or do just 1 slow hack or sometimes a lesson in between. If icy or otherwise bad footing prevents work other than walking, then I walk them for as long as possible until I get too freezing cold or run out of time for the day, whichever happens first.
Most of the people I hunt with keep their horses in similar situations, so if weather interferes with fitness work, we are all more or less in the same boat. And to be honest, most of the folks I hunt with worry about fitness far less than I do and rely on hunting or hound exercises 1 or 2x per week (plus 24/7 turnout) to get and keep the horses fit. Many of their horses have been hunting for a decade or more and are completely sound, so that strategy obviously works for many horses. The additional days I work my horses are just as much (or maybe more) about the fact that I’m hoping they will be event horses in the future too, so we have to do some dressage schooling incorporated into our hacks.
I agree with tangledweb it is better to get out now and hunt while everyone is working on fitness rather than trying to wait until later in the season when the hunts will be longer and faster. If the hunt becomes unexpectedly long or difficult there will likely be someone willing to hack in early with you.