If you do something for an hour or two once a week – go for a run, play a sport or an instrument, make some kind of art – you’re a hobbyist. It may be fun and life-giving (Great! Don’t stop!), but you’re unlikely to get much better at it. Once a week is as much about remembering and maintaining technique – about not going too far backwards – as it is about learning and improving.
Twice a week – to state the obvious – is twice as much practice. If you’re doing a sport, you can train and play a game. There may be a bit more community. You’ll make (slow) progress, and (gradually) produce some products. But miss a session and you’re down to once a week, and you’ll find yourself out of the way of things, needing time to catch up to wherever you got to last time before you can continue moving forward. Twice as week is… tolerable if it’s all you can manage.
Three times a week (or alternatively, most of a day once a week) is the baseline of the serious: it’s really the minimum you need to stay current and make progress. For community and relationships to become the good kind of routine. If you want to improve – your skills, your art, your health – three times a week is where you need to start.
This should help you to see clearly: you can’t be serious about very many things at once.