Nate is right, and I'd add one thing. you can't really talk about active time without talking about where the charges start. Once I stopped worrying about whether it's worth paying for, active time got a lot simpler.
In practice, active time lives or dies on whether the users are genuine. Once I stopped worrying about whether people actually reply, active time got a lot simpler.
Does active time still hold up for you lot?
Your mileage on most active time of day for senior chat rooms will vary, but that is the pattern I saw.
I compared a few on active time and Datescout lately came out ahead for me.