What age did you set a bedtime hour??

I currently have a five month old who takes three naps a day, and generally wakes up anywhere from eight in the morning to nine in the morning. Her naps are somewhat inconsistent sometimes 30 to 45 minutes or others at 1-1.5 hours.

This leads to bedtime being anywhere from 7:30pm to 9:15pm...

So my questions are...

Did you wait until your LO went to 2 naps? A certain month? Did you set the time or did LO? What's your LOs schedule like?