Deciding how often to rebalance when contributions already shift the allocation

I contribute to the same broad funds every month, and those contributions naturally pull my allocation back toward the targets when one side has fallen behind. That makes me wonder whether scheduled rebalancing trades are necessary at all while the portfolio is still small relative to new savings. I don't want to micromanage percentages or create avoidable taxable sales. Do you use a tolerance band, an annual check-in, or just direct new contributions at whichever holding is underweight?