Can we start anytime? Rebalance anytime?

Seems like people tend to rebalance at the end of each quarter.

I’m new to this and I’m just wondering if I started it today for example, 60% TQQQ, could I plan on rebalancing 90 days from today instead of June 30?

Also, can you rebalance at key moments instead of an exact date? Like after QQQ makes a 5% move in either direction?