Can't Last Long Should I Let Her Explore?

So I use to be able to last for a long time 30-40 mins easy but for the last year I'd say I can barely make it maybe 10 minutes if in lucky. My wife has a high sex drive and hasn't really been into the sex. Not that it's not good cuz she loves the foreplay we have and the sex for however long it lasts. But she's never done when I finish. She's got this one ex boyfriend she loves having sex with. He was rough and lasted a long time and would make her cum multiple times like I use to be able to. Now we talked a little bit about her finding another guy and exploring to "get her fill" now it would be protected and safe and only for the sex. She would only want to have sex with her ex because she feels comfortable with him and doesn't want a stranger and add to her "number." We still have great sex sometimes I mean we play and are kinky and sometimes I do last a long time and am able to make her cum atleast twice once in a while. And she says she is satisfied with our sex but sometimes I feel like she doesn't tell me she isn't cuz I know I'm not all the time due to my issue well call it. Now my question being, should I condone this and let it happen so she can have enjoyable great sex again? And how can I last longer again?