I used to do it daily (some times twice a day!! I had a girl who was clueless at free play and if wasn't occupied she was trouble!! Lol) but have cut back to 3-4x a week. In the summer however, it's more like 1-2x a week as we just aren't inside long enough some days to bother getting it ready and put out.

Some times I'll just tape paper to the table (ikea sells a huge roll) and put out markers and crayons and they can come and go as they please.

I would love to have more out and have it come and go all day but I've never had an old enough group to safely do this