Can I back up my iPhone 5S to more than one MBP? I have a 5S that's backed up to my home 13" MBP, as have every other iPhone before it.

I am getting a 6, and want to back up the 5S to restore to the 6.

I have a second MBP, a Retina 15", at work and I'm wondering if I can simply back up the phone to this Mac and restore from there -- so I don't need to drag the home MBP to work.

Can I back up my iPhones to more than one MBP?
No, your iPhone can only be associated with a single iTunes Library. You can, however, copy the backup folder from you MBP to somewhere else. It will be in

~/Library/Application\ Support/MobileSync/Backup/