12hrs is well within the average amount of sleep but also worth bearing in mind that LOs this age have such varying sleep needs and varying routines. Some have already dropped the nap completely whilst others hold on to the nap for another year or more.
The age period you've stated is exactly when my DS's routine needed attention. For us attempted nap capping didn't work and neither did the occasional no nap day, both totally normal methods moving towards total nap drop but neither suited him at all. So we began that age period on 2hrs sleep and about 10 or 10.5 hr nights, nights went shorter and shorter (hence my attempts to tweak and cap) until it was more like 9hr nights. At 31 months he dropped the nap cold turkey and moved to 11/12hr nights. So whilst the changes in DS's routine were showing clear sings for several months the real change happened very very suddenly.
Our routine when it was stable was
WU 6.00am
Nap 2pm - 4pm (2hrs)
BT 8pm