I think that photo roll thing amounts to a "wives tale". The only way to reduce the back-up time on the iPhone is to NOT do it. Refer to the following link:
If no change whatsoever, there may be a problem with the backup which includes a significant amount of data.
Go to iTunes > Preferences. Under the Devices tab select your iPhone's backup followed by selecting Delete Backup.
To manually create a new backup for you iPhone, right click on your iPhone in the iTunes source list and at the menu window that appears, select Back Up. An entirely new backup will take longer than following updates to the backup.
Sorry, but Apple doesn't post such a document that is a "wives tale".
My iPhone's backup has never taken longer than 5 minutes at the most, and this dates back to my original iPhone that purchased on the release date and used for over a year, and with my 3G which was purchased two years ago this coming August.
I've got a two year old 3G and had an original iPhone that my son still uses. When I sync my phone that has about 10GB used, the backup takes about 30 seconds, the entire sync process takes about 1.5 minutes. The only time it has taken significantly longer than that was when I got the 3G replaced for a warranty issue and the first backup after the setup took longer. Been fine ever since.
While disabling the backup as you describe may quicken the sync process, it just puts you in a risk situation of not having a backup to rely on if you should need it for a restore. Also, since iTunes backup has to do with changes since the last backup, the more you disable it, the longer it will take because it will have to create an entire new backup.
I assumed the same thing (incremental backups), but when EVERY backup takes 3-4 hours, it's obviously not doing what it's supposed to. I don't know your specific iPhone config, but I think the amount of email/calendar/contacts data has a significant impact, and when I see a lot of folks having the same problem as me, Apple obviously needs to re-think the process. Also, notice I recommended ONE GOOD BACKUP (which can be repeated at a time of your choosing), but waiting 3+ hours every time I try and sync a new app just won't work.
Backups should not take 3~4 hours, no matter what your phone configuration or computer you sync with. I manage numerous iphones(all 3GS) on numerous computer configurations and NONE of the iphone backups take more than 30 seconds, max. If things get beyond that I start looking for causes. The three biggest reasons are(in no specific order): 1. Corrupt backup on your computer, 2. Apps on your phone that mismanage data, & 3. Photos in your camera roll(they should be imported regularly). So, start some troubleshooting and identify your problem.
I have the same problem. I have an iPhone 3GS 32g since november 2009. At the beginning the sync take 5-10 minutes, then 30 minutes, then 1 hour, then 2 hours, then 4 hours... now i'm at 6-7 hours! Wow. I have practically the same amount of data in it. iTunes have a bug in the software and need to be corrected. This bug begin with the war between Palm Pré syncing with iTunes and Apple. Do you remember the number of update iTunes do to block Palm Pré against syncing with iTunes? Now we pay for this!!!! It's a big issue need to be corrected fast. I hope before OS4. Please help us.
If this were true, then every iPhone would have this problem, which is not the case.
What have you done if anything such as removing all photos and videos from your iPhone's Camera Roll after being imported by your computer per the link I included with my first post in this thread? If no change after doing so, have you tried deleting your existing iPhone's backup and manually creating a new backup per the instructions I included with another post in this thread.