Best time: when you are ready to make more money. I’m among the highest in my area for s/s, touchless, and vac. I do what’s right for my biz. Always keeping equipment in working order and always taking care of calls and issues. It’s been two years since I raised my vacs from $1 to $2 and the time from 4 to 6 minutes. Even with a doubling of start price, I’d have to loose 1/2 of my vac biz and that was unlikely and in fact my vac biz is up with less mess.
I do not “warn”of a price increase. Not like a customer can stock up. I do change out my price signage with new professional decals with the new pricing etc.
I’ve never regretted a price change. I’ve also always gone with a price increase as opposed to a time decrease