In Z6, I would be tempted to plant them in Spring in the ground so they are somewhat prepared for your cold winters (so keep them in a protected garage once dormant and water them every week or every 2 weeks).

I don't have any intentions of planting these in the ground. I plan to keep them in containers. I just wasn't sure that newly rooted cuttings would survive dormancy in the garage at all, or if they were better off staying in my kitchen windows through the winter once they're potted.

I have 6 in the ground, but I am concerned about their longevity due to all the silver maples in my yard.

I kept my cuttings in the house in the unheated attic window over the winter. Just a little warning though about half of them will go dorment anyway and lose their leaves. Every single one came back up for me in the spring though.