Let me ask the question specifily for those in my climate zone? What are some of you other northern beeks doing?
Here in central Ohio, I plan on putting on 4-6 pounds of patties in early-mid March, and checking patties in early April to make sure the bees still have patties. If the bees run out of supplement, they may throw out developing brood, and it may slow the queen down, and I want to avoid that.
When I put on patties, I will check stores of honey and feed syrup as needed.
Ideally you put on patties 9 weeks before dandelion bloom, and dandelions are often blooming by the 3rd week in April, so you could get away with putting on patties in late Feb. But life isn't ideal, and I'd rather wait a couple more weeks to let brooding begin to lessen the chance of the bees being unable to cover all the brood in a cold snap and losing brood.