Week days might need shorter sessions where as week ends give you more space.
If you are new to tantric sex, I would definitely start with short 15 min sessions max.
They can even be shorter to 5 or 10 min.
Check with your partner and make sure you agree on a time frame.
It's important that you check if you or your partner have to leave soon or if you have plenty of time.
In my opinion, having frequent short sessions works slightly better than one long 2 hours session once a week for instance.
Think of the way you eat for instance. You have a meal or snack every 3 hours, right?
Or when you train your body, you build up your level of fitness by exercising every day for an hour rather than just running a marathon on Sunday, right?
Tantric sex is an energy you build following the same type of principles.
You can build up tantric sex energy a bit in the same way, by having short tantric sex moments throughout the day or the week.
Of course, a one time long practice in the week end is totally an option too and will work perfectly if that's what you prefer.
It's essential as well to always check with yourself and your partner to see the time that's best for you two.
Is it day time during the week, week days evenings, evenings in week ends, middle of the night when you feel a desire rush?
Timing is super important and identifying what works best for your couple will strongly empower your tantric sex practices.
Once you are comfortable with short sessions, you can extend these sessions to 30 min and eventually 1 hour or a few hours.
It could easily take you a couple of months to build up your energy to the point where you can easily go for a 2 hours tantric session.
Remember though that you want to leave on a high with the feeling that you could easily go on if you wanted to.
Many people who start with tantric sex will make the mistake of wanting to press all the juice out of a session.
They experience a bit of the tantric bliss and don't want to let it go by fear of not being able to recreate that experience again.
Remember that the goal is to be able to play with your tantric sex energy at will.
You can trigger it any time you want and even play with its intensity.
That's one of the core targets of tantric sex.
To your tantric sex power!