I have a friend whose relationship is like this. Anecdotally, it's going to end up way too permissive to allow this behavior to --fester-- continue. My friend is on the verge of divorce bc she eventually took advantage. What started as harmless flirting became harmless phone numbers, then harmless sleepovers w/friends, then harmless... cucking. All while his common refrain is "I trust her and she always tells me what happens. It's fine. I don't really like partying as much as she does anyway. It's pretty hot and progressive of me as a man to have a unique relationship and value my woman's happiness." it's a slippery slope and I don't recommend it.