Yes, that's the other thing, the cues come out if they're bored too, so that's why you watch the clock til close to nap time. Maybe also change to one of a few pre-nap activities/locations?
I think they're almost caught up to the normal A time for their chronological age, really, if they're up to 3:25 (which I think they might handle ok given what you've written). I do think though that keeping the A time the same for a week once you've done this amount of increasing is important just to make sure you're not seeing a temporary decrease in nap length which can happen before they lengthen back out again on a new time.