It does seem to me like people are being a little harsh with their responses. I'm from near ORD (and have a dotcom startup company also based in Chicago), went to undergrad near LAX, and currently am in grad school an hour from LHR (probably back to LAX in another year). For part of all this I've also had a girlfriend "back home."

While I never flew back once a month, which it seems like you're going to attempt, I certainly was/am flying back and forth every term and occasionally for something in the middle of a term. For me, it made a great deal of sense to figure out which airline seemed to have the best fares on those routes and--all else being relatively equal, of course--stick with that one. (The adjustment I use is that frequent-flyer miles are worth roughly $0.01 each to me.) AA almost always has the cheapest LHR-ORD flights, and it doesn't take very many of those roundtrips each year to get a lot of miles--particularly having done the Gold and Platinum Challenges, which I never would have heard of if not for FlyerTalk.

So, I think it's worth it to at least consider the reward programs, and you're being smart by planning ahead if this is what you really intend to do. From my perspective, they make things cheaper... every 4th roundtrip or so that I take (which would be taken anyway) across the Atlantic is free.

I've never viewed grad school (I'm in my 3rd year overall, though that's at two different schools) as a necessarily monastic experience. I don't think I could do it if it were! Quite frankly, if I didn't do some travelling and other things to make sure that I wasn't feeling isolated, I'd be miserable. If my "lack of focus" means that I don't finish the PhD, that's a good sign that I'm not cut out for a research career anyway. If that happens, I'll just go work for McKinsey or something and *really* rack up the miles.