DD1 transitioned around 14 months and would usually do about 3 hours.

DD2 has just gone 14 months and has mostly been doing one day nap for a good month or so. I find she does best if I put her down around 11-11.30 and most of the time she sleeps for 3 hours. If she's had a bad night or started the day earlier than usual (or both!) I put her down for 2 sleeps that day but I do find she's up later that night.

It's a fine line at times! I'd suggest you try one day sleep though.