After I'd fucked him a couple times that night my husband asked if he could watch my ex fuck me because he'd never made me orgasm as hard as my ex did, so we let him watch, now he invites the ex over about once a month to fuck me again and I love it.
Remember, when making naughty bets with your husband, let him win some of the bets and offer up a hand or blowjob from one of your horny girlfriends, just remember you may have to do the same for her sometime, lol. If you do this for hubby he'll love it and it's one step closer to opening up your marriage as well.
If you don't have a friend that will give your hubby a hand job, talk her into watching you make your husband cum on your titties, hopefully she will join in at some point if you coax her while you're doing it