Switching to one nap

At what age did your LO switch to one nap a day? Did they eat lunch before they laid down?? My daughter is 18 months and has been consistently taking two naps (generally 1.5-2 hours each) a day for a year now. She seems to be spreading her first nap to later, which causes her to not be tired or fall asleep for her second nap time, so I’m wondering if we may be switching to one nap a day soon🤔 do I hold her off until after lunch? Or should I continue with our normal routine for a while and see how it plays out? Is there an advantage to switching to one nap? I’m pretty sure she would just stay on our usual schedule if I pushed it, but I’m trying to follow her lead. Her bedtime is 8:15pm and she wakes almost exactly 12 hours later the next morning.