I ended up with a reserve trip to EWR with a layover and DH back to IAH. I left layover hotel 3 hours early to go in and swap it out. It took 2:20 to do it.
My suggestion is to have them pre-loaded with what a 737 pilot needs, 787, 756, etc. Have them fully ready with Jepp and WSI and content locker. After the pilot walks up ask him or her what fleet and then simply load a profile and an email and assign it. Wham-bam, done in 10 minutes.
The Techies in EWR said that yesterday it was taking 3:30 to 4.0 hours due to bandwidth restrictions. If you log on to the nearby United Club First Class lounge wireless it will be much faster. Likely about 2 hours.
Reportedly the Techies were just handing out the Ipads after profile loaded and getting you to re-load it all at home or at the layover. But, you'll need to leave with both Ipads and turn in the old one, once everything properly loads.
I jumped up and got it done in 2:20. But, when I left I saw pilots still hanging out who were waiting to get finished, and they were there 30 minutes ahead of me. If there were a CBT lab or something there you might be able to better use your sit time.