You "should" wait between sessions but I would find that life got in the way and then I would never get back to what I was doing with my wee one. So I would set aside time in the morning and then find time again in the afternoon to specifically do flash cards or EL sessions. In each I would do reading, maths & music. I never did achieve 6 sessions/ day of doman dots... I ended up doing as many as I could fit into the baby's interest period
I like the sit down times but it was easier to just include EL throughout your day and make whatever you are doing an learning opportunity. E.g. We have a map tablecloth and my 2 year old thinks it's really funny that she has her lunch at the north pole with the polar bears whereas her brother is way down in Antartica with the penguins:-)
Whatever works for you, as long as you are exposing your child to knowledge they will learn despite any mistakes you might make.
Hope it's going well for you,