> I fear my urge to try someone new (and hence cheat on my partner) will be pretty strong

I am the kind of person that will stick with anything if I love it. Even with escorts if I find one that I really like and she really stands out I will go see her exclusively until things change. I won't feel the need for variety just for the sake of it but I know not everyone feels this way.

I haven't tried this but there are people out there that build "harems" while being honest about it. If you truly can't live without variety and are confident in yourself you will find a girl that wants an open relationship or maybe you can find someone bisexual that can enjoy variety with you.