I commuted from CMH for about 5-6 months. However, as I was the second from the bottom in my new-hire class, only LAX 737 was available. I can tell you the CMH-LAX commute was pretty rough, simply because it was so far. It helped tremendously that I had a line my second month out of training, but it sometimes took all day just to get out there and back. I'm in ORD now, but I have since moved to Chicago to avoid the commute.
I would suspect you could hold ORD within your first year. Long call does make it possible for you to sit at home during RSV, but you could easily be converted to short call, and if it happens late in the evening, you're running the risk of not being available for short call, unless you plan to drive it through the night. We do have the ability to 'agressive pick up' trips the day before a RSV period/day, so as long as there are trips available, you can pick up trips that fit into your RSV block minus 1 day. For example, if I was on RSV for 4 days, I can pick up a 3-day or 4-day trip. This significantly increased my QOL, as I could actually plan to commute to an actual trip, as opposed to commuting to sit RSV. EWR and DCA are both slightly less senior than ORD, and although I have not checked reserve levels in those bases, I imagine you would be able to hold a line a bit quicker there.
Having said all that, I have talked to a few people doing the CMH-ORD commute, and they all seem to say it's fairly easy. Between UA and AA, there are a lot flights, and it's a short hop. BUT these were all people who were holding commutable lines out of ORD, which makes a big difference. I think as long as you realize for your first year or two, the commute may not be ideal, but with a long-term perspective, one or two years is but a drop in the bucket... unless you're 63 years old. =D Good luck with the interview! I came from the regionals, but I have really enjoyed my time here at UAL, and the crews have been such a pleasure to work with.