From my experience the "estimated time" depends on the size of the file being downloaded. There are very large .vdx (i think) files that consist of major new content (i.e. zones) While they are d/l the estimated time is VERY high, for me like 5-10 hours (i have a very very fast connection)
however, once that file is done, and the patcher has moved on to smaller files, the time drops significantly; only to go back up when another large file is being downloaded.
Hope this helps. The be all end all is that you *will have to d/l the patches and you might as well start now. now, start now. NOW!!!
sorry, got a little carried away.