[zeroxfe]

If you're a beginner, you'll need to work your way up to at least 45-minute sessions. You're not going to be able to enter jhanas in 20 minutes unless you're very experienced and entered them consistently for a long time. For me, it was when I got to 1 hour sessions when I started to experience the deep absorption for jhanas.

[swayvil]

I find that multiple sessions is the way to go. not necessarily longer. Like, dedicate 3 days to chill stuff (walking, cleaning...) and meditation. Meditate, say, 6 times a day for 20-30 minutes. That'll do it. Fasting helps too.