Before you entered the lifestyle with your wife, did you have lots of communication and lay down ground rules including stopping? If not, then you better do it right away. Without ground rules your marriage could go anywhere
And if it is not working out the way you want or envisioned, then you are the author of your own misfortune. Your wife didn't want to but you kept pushing and then she relented. And now she really enjoys having another cock inside her? Well that is what you wanted.
I can tell you this, One your wife has had the freedom to fuck other guys, especially if they are bigger, fill her up better, reach all the right places and have more stamina and maybe are just better lovers (foreplay, kissing, cuddling etc.), she ain;t going back to you. So even if she "stops" she may start getting it on the side and not telling you.
Sadly sex is an extremely powerful emotion and once you let the genie out of the bottle, you can't control it. So you may end up being a cuck whether you want it or not.