This is definitely something to address with your T before starting EMDR. Ask them how long the sessions would be and if there is "down" time factored in where you can regain your composure.

I think that if your T is experienced in EMDR, they know to leave enough cushion time between the actual "work" and when the session ends.

My T told me early on that 90 minute sessions are available if I need them. I just need to let him know when I make the next appointment. Sometimes I've even changed my sessions from 50 to 90 minutes the day before my session.