If high quality hay is your goal, don't delay harvest. However, if you're looking to rebuild your hay supply, letting it grow almost until bloom will provide more feed while using water resources more efficiently.
No-till seeding alfalfa can help preserve crop residue on the soil surface, reduce soil erosion, limit weed seeds on the soil surface, and perhaps most importantly this year, help conserve soil moisture.
Bitter cold spells and desiccating winds in early winter may have endangered alfalfa stands. Evaluate alfalfa stands soon to determine their viability and the potential need for replanting or rotating to another crop.
With temperatures beginning to warm up, now is a good time to manage weeds such as field pennycress, downy brome, mustards, cheatgrass, and shepherd's purse in dormant alfalfa without risking plant injury.