I see your point but I'm not jacking up my electric bill any more than I have to. I'm a subsistence grower.
Where does your RH peak at lights off without the fans?
I can do this during Veg, but once they get big enough if I cut the fans at lights off the RH spikes at like 90%. Although, this is a tent in a closet so I don't have the same air flow you do.
For shits and giggles though, a 4" inline fan run for 24 hours a day, rather than 12 hours a day, costs (at $0.15 per Kwh) about an extra $0.22. Over the course of a year that's a whopping cost of about $55, or less than $5 per month. I don't know about you, but I can spend more than $5 in a single trip to taco bell. Fans on for me