Depends on what version you are coming from.
Also how many computers need to be upgraded.
If you are already on 6.3x, Probably about 1.5 hours main computer, 30 minutes for the others, which can be going simultaneously.
Main one takes longer because you may have SQL upgrade and you need to have it running so you know the others will have someplace to connect. You could run all simultaneously but if it fails at the main, going backwards is a major pain.
