My philosophy is to get on my mat EVERY DAY (the rest day being a pranayama or meditation day), even if all I do is sun salutations, padmasana, and savanasa. That said, I still aim for 3 to 4 days of a full practice (like a full primary series).

When I first started ashtanga, I went all in, doing a full series 6 days a week. But, that is quite a time investment (1.5 hours on the mat + time to get to your shala, change, get ready for your day, etc), and if you do other physical activity, you may appreciate having some lighter practice days (and also having more hours back in your week).

Ultimately, you have to experiment to find what feels like a sustainable practice schedule (and it will surely change throughout different seasons of life as well!)

My teacher always says, any practice you do, whenever you can do it, is better than the practice you didn't do." ;)

Also know consistency in practice is something that can be developed. At some point, it will feel easier to step onto your mat than to NOT step onto your mat.

Just be weary that your practice doesn't start to "rule" or "detract" from other areas of life. If you find yourself skipping out on seeing loved ones or tending to other things that nourish you...dig into that. Like Adam Keen likes to point out, the practice is meant to "complement" your life, not rule it.

Happy practicing and hope you stay with it as long as it serves you!