How often should someone actually review and rebalance their portfolio when accounts are this small? Monthly? Quarterly?

Quarterly is about right for most people. Monthly is too obsessive and costs mental energy. Yearly is too infrequent and lets drift get out of hand. Pick a schedule and stick to it. Set calendar reminders so you actually do reviews instead of forgetting for eight months then panicking.

I was checking mine constantly, which drove me insane and led to impulsive changes. Eventually settled into quarterly reviews every March, June, September, and December. This rhythm worked perfectly because it coincided with natural seasons. Made the process systematic and removed emotion entirely. This guide helped structure my approach: https://brokerseed.com/en/3k-investment/