Hello okhud,
If there is one mistake I made when starting out, it was to over do things. I saw my little baby staring at the cards with the greatest curiosity and I would spend lots of time with them, only to have him not interested the next day
I'm not saying all babies respond the same way, but if I could have it over again I would treat any kind of teaching like I treat candy, I'll be incredibly stingy, only let him have a glimpse and then downright refuse to show him anything again for at least an hour. Building up to more and more later, but always have him feel that he would like more.
Doman's advice is to stop BEFORE (not when) the child wants to stop and that many very short sessions a day is better than any one long session.
Sorry for this long answer, I'm feeling like discussing EL today
In short, I'd say only play the session once in one sitting. You could always play it once every two hours, but even that could bore your child in the long run, twice a day is great, aim for EVERY DAY. And if you feel your child wants more in one session the you could always download some stuff off the library and use them instead of repeating the same stuff over and over.
Kind regards
Carla