How often do you walk him?

For those of you who take your cats out on a harness, how often do you do it? I am trying to adjust my Sammy to indoor only (for the third time) And have been taking him outside with supervision once in the early evening.
He yowls at the door in the morning but I am ignoring it, he is giving up pretty easily(yay!). I don't want him to "learn" that the louder he gets the easier I will respond so I want the going out to be on my terms.

why not a walk every day ... or a few times a day

I only walk mine once a week, I don't want to get them too used to being outside.

No set schedule, but we try to take her out at least once a day before and after the heat kicks in for about half an hour.

At least once a day for our two Bengals...they have too much pent up energy to burn, and they love it outside.

Thanks everyone, I am aiming for once a day. After work is a good time, I think that should help.