When they drop to one nap--usually between 12-18 months, things get a lot easier. For some LOs who are sensitive to OT, you still have to be pretty careful of A time, but because it's only once a day you're getting them down and because the A times are much longer, you have plenty of time to go out and do something and get back in time for a nap, so you lose that "on a timer" feel.
Guarding your LOs sleep is something that never really ends because we live in such a crazy go-go-go society, but as their sleep consolidates with age, it gets easier to manage. My almost 4 year old has dropped his nap, but I still have to be careful about his bed time. His dad wants to take him out and do stuff in the evening sometimes and being a little late to bed once a week is no big deal, but several days in a row it adds up and starts to affect his behvior.