I check our itineraries once a week. Most changes have occurred over weekends with the most common time for changes to occur being at the first of the month. With each "sweep" we lost seat assignments, especially for award tickets or for upgrades. Indeed, award tickets were totally cancelled once. E+ seats are routinely replaced by E- seats. We are usually able to recapture the lost seat assisgnments, or something similar, if we respond to the changes early. We have never recieved any notification. One flight, booked 9 months early, underwent 8-10 changes (5 min time changes, flight number changes, equipment change, inadequate layover times, and switch from non-stop to a one stop flight and back again). We did not receive ANY notification at any time. Pre 3/3 merger a quick call was all that was needed to recapture seats. Post 3/3, we haven't been very successful.