Wirelessly posted (BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
You should be able to check current award availability for your dates of travel on both aa.com and united.com. Although award-seat availability can change by the minute, seeing what is available now for next Spring might help you decide which miles to pursue.
Also, keep in mind that both AA and UA miles can be redeemed for one-way travel, even on their partner carriers; so you might end up using AA miles in one direction, and UA miles in the other, depending on award-seat availability.