I think, from a dudes perspective, you kind of know if you are long term compatible once you get a good look at the flaps and b-hole. Other than personality- honestly there are lots of cool chicks around so let's assume you are smart enough to weed out the turds and get a decent mate- you gotta find a decent grundle. And to each their own. I prefer ham to roast beef. Others don't. Some peeps like a big brown eye, some small, some less brown, some pure stank. But I think you kind of know it when you see it, despite the personality thing. Like, I can deal with this or I can't or I want different, even if its the coolest mate in the whole world, the grundle could be a deal breaker or just like a sign, this one is or ain't for me. Like soul mate type thing.