My guess is if you write an Investment Policy Statement, it should:
1 include an annual evaluation of your asset allocation, and some rebalancing toward a target that matches your goals. For example if you decide that 60% stock 40% bonds is the target because it will let you sleep at night but also grow over time, and on Checkup Day your portfolio is 53% stock, your rebalancing target would be “add 7% stock.” Or if 50/50 is the most stock you can stand, the IPS has 50% as the target; on Checkup Day, you determine the new goal is “3% less stock”.
2 include a procedure for doing the rebalancing. If taxes don’t affect you, maybe you sell and rebalance immediately. If tax minimization is important in your case, maybe you just direct all upcoming dividends toward the category that needs investment. Design a procedure that meets the needs of your situation.