My wife tries always to keep a lover but then also has (for the most part) a small stable of fuck buddies, her current lover S she has been with 11 years, prior to that K was with around 8 years there have been a couple of others that were both 3 to 4 years....
So how it works for us is that S her lover takes her away over night once a month to a little remote Air B&B then occasionally if he is passing he will stop in for a quickie....then she will see a fuck buddy a couple of times a month, then she has a girlfriend L nothing sexual between them, but her and L will on occasion go off to swingers clubs so whilst there sometimes she does and sometimes she doesn't so 3 ish times a month on average...sometimes 5 sometimes 2...
As an aside....
So for those new or who haven't quite got there yet it all sounds ideal and at present it is, however we are 30 years together and 28 years as a cuckold couple, it doesn't just happen over night unless you are really really lucky......there have been times where she had only 1 fuck buddy and no lover, there has been cross over where she has had 2 lovers and on rare occasions, times where there were no fuck buddies and no lover....and we are human so illness, holiday's and all those normal non fantasy real life things can sometimes get in the way and stop play.....but don't let any of that put you off when it's right it's right and not a lifestyle I would ever look to leave......Good Luck!