OP, I'll second what everyone said about upgrading glass - consider how much you spend to directly correlate with how long you can spend behind that glass before getting fatigued. Anyone who says otherwise is either honestly ignorant or lying to themselves to feel better. And, look for used Swaro binos in the optics classifieds - a set of ELs or SLCs is better than anything you've got, and won't be too terribly bad on the wallet. A lot of guys have been selling theirs off as they upgrade to the Swaro NL Pures, so it's an excellent time to get a great deal. The first piece I'd upgrade, and the place I'd always put the most money, is the set of glass I'd spend the most time behind - the high-power binos.
The only other thing I can offer is to remember that your eyes have a lot of muscles in them - spend time building that up before the season. Even half an hour every day of practice glassing will help, even if it's just birding or looking at other wildlife. Just try to get the consistent time in, and grid inside the glass the same way you would grid off a hillside looking for muleys, so that your eye muscles are getting worked just as they would during season.
