How long would it take to enter 3rd and 4th Satipatthana? Let's say I am meditating for 2-3 hours each day. How long would it take?
How long would it take to enter?


That's like asking how long would it take for you to start tasting the curries that are already on your plate. Or like asking how long will it take for you to taste almonds and cashews when you are eating a mix of nuts. It's just a matter of you deciding to practice awareness on them.

Cittanupassana

When your mind wanders thinking about past/present/future or when your mind becomes concentrated/scattered, you can be mindful of it to practice the 3rd Satipattana

Dhammanupassana

If you decide to practice mindfulness on seeing, hearing, smelling, tasting etc. or the five hindrances, that's the 4th Satipattana.