This is how I use the addendums:
With a ball pen I write all the important information right on the map. Motels, hostels, B&B are not of interest to me so it boils down to route changes, campground changes and closures/operings of grocery stores/gas stations. That way I don't have to fiddle with 1 extra sheet of white paper pr map when touring. I always did it like that, and I love it. This swapping of information to the maps takes me approx 1 day and is worth every minute spent.
I will be doing the Transamerica starting June 2nd in Washington DC. This is a late start as a realize that many cyclists start in May, maybe even April. Those cyclists will be just ahead of me and able to report on any changes to Missoula.
At the moment I see some addendums from February 2012 already which is good. However, how is the procedure for updating the addendums? If a cyclist reports a change on route, will it just be added instantly without any ACA research?
Just prior to departure things get very hectic for me and I will not have time to print all the information onto the maps the night before departure. So when would be a good time to download the addendums? If the addendums are truly updated instantly I have to pick the latest time possible. If there is a 1 month "processing" time I can relax and have it done a quiet weekend in May.