Originally Posted by
expressboy
If both the tickets are on UA you should book them separately. I have never had an issue with checking bags through or getting reaccomodated due to delayed flights even on separate tickets. For your peace of mind look for ~3hrs to connect at the hub if one of the legs is international.
Another suggestion if you go this route is on your outbound, book an overnight stay at the connecting hub. This makes it much more likely that you'll not miss the long-haul flight, where the next option very possibly is the next day. On the way back, a missed connection is often much less of an issue: you're going home, so you don't have non-refundable hotels, tours, and other plans to worry about, and there are likely multiple flights a day back to your home base or another nearby airport.