Our LO used to have 3 naps for this reason. He would nap in the morning (around 9am) then in the afternoon at around 1pm. He would then take another nap around 6pm.
When he did this, he would wake up around 7pm so then would only go down for the night around 9:30pm, but that was fine with us.
He only this week cut out that evening nap so this past week he changed his own schedule, and goes to bed at 8pm, 8:30 the latest.
So yeah, we basically just went by his cues and let him sleep when he wanted to sleep, even if it meant a dreaded 6pm nap. Eventually he just stopped on his own and now sleeps 8pm-7am or so.