I had a coupon good for $10 in free slot play at the Wigwam Casino (two blocks from my house) with purchase of a meal from the Wigwam Restaurant, so yesterday morning, I walked up and had lunch (actually a late breakfast) there. (Lisa is still trying to get over a cold and told me to go enjoy myself.) The meal was $13 including tip. After eating, I showed my restaurant receipt and they applied the $10 free play to the machine of my choice (in this case the blackjack machine). You can't cash out free play; however, after running through $10 worth of bets, I found that there was $13 on the meter. I decided to not be greedy and cashed out.
I think that's the best conversion of free play to spendable money I've ever managed. And the food was pretty good, too. Thanks, Wigwam!