when my lo was about that age (about 14 or 15 weeks), we did a 3.5 hour EASY. I did it because she was staying up for almost 2 hours at a time and wasn't hungry after 3 hours. We then went to 4 hour EASY at 16 weeks so that it wasn't this big switch.
I need to read my journal to see what our routine was like and how much she slept, etc. although my lo always needed more sleep than the average (like i am or at least used to be).
could you post your routine and maybe we could try and redo it a little for a 3.5 hour easy and then maybe in a couple of weeks, try to redo it again for 4 hour easy.
just to let you know, sometimes it takes a few days to adjust to the new routine. my lo got overtired after we moved to 4 hour easy and so she didn't sleep great at night for a week (after not waking at all for a few weeks, she started waking once or twice during the night). neither of us really knew how long she could stay up. we're going through that again right now because she's wanting to nap less now during the day.