Hi there - welcome to BW forums
Here's a couple of links you might find helpful:
Time to Transition - 3hr, 3.5hr or 4hr EASYAverage A times- BOOKMARK ME! I would like to transition my 3.5 old boy from 3hr EASY to 4hr EASY routine. Do I have to follow the 5 min interval transition plan?
No, you do not need to move in 5 min increments, some people find this easier if their baby is particularly sensitive to increasing A times but some do not respond well to only a 5 min increase.
It's not so easy to see from your EASY times how long he is sleeping for each nap but if the naps are shorter than 1.5hrs, and if he is an independent sleeper (usually able to fall to sleep without help and usually able to transition between sleep cycles without help) then an increased A time may help to extend the naps or will help you to re-settle him more easily as he'll be that bit more tired.
I would suggest increasing the A by 15 mins (to 1hr 45) in the first instance, and move E towards a 3.5hr interval.
During the transition phase you may need to help him re-settle during the nap, either because he becomes a little OT and wakes after a short nap, or because he needs to be taught the habit of sleeping longer (ie to transition rather than get up when he wakes).
After a few days, if you feel he is ready to go to a full 4hr EASY routine you would increase the A time by another 15 mins. Not all LOs go straight to the 4hr EASY and may stay on 3.5hr for a while. You can always post for advice if you are not sure.
Does that help at all?
Have you already tried the transition?