We went to one nap when it started taking an hour of nap resistance for the first nap and a flat refusal for the second. Then they'd be OT. Bedtime was a nightmare and multiple nw's. Dropping the one nap was a little different. They would happily nap but bedtime would sometimes take 2 hours. Multiple nw's, long nw's and ew's sometimes of 4am. Then we pushed the nap back to 10am but they were just getting caught up for the next night to go at it again. Funny when I write it out it seems to make more sense now. We still get some nw's and ew's of say 6ish but things are waaaaaay better. I think there's a lot to be said about temperment too. I really think spiriteds fight sleep. Mine always did no matter what the routine almost as if theyreafraid of missing out on something kwim? E only fights if she's severely OT.
Going to one nap took about 2 weeks to see a good change and there was a lot of tweaking to routine along the way. Dropping it entirely was easier routine-wise but took longer to see results.