Hi there G and welcome to the community. Yes, it's fine to split your LifeFlow sessions to 20 minutes in the morning and twenty minutes later in the day.
One thing to be aware of is the 8 minutes it initially takes you to entrain to each specific level - here is a post from the golden threads section which will explain the 8 minute rule clearly for you:-
A Question about Entrainment for the Experts!
Hope this helps and I wish you much peace and joy