A few days ago Stuart Langridge and I upgraded a machine from 8.04 LTS to 10.04 LTS and then from 10.04 LTS to 12.04 LTS, all over SSH. Both upgrades ran without a hitch. We simply ran
do-release-upgrade and everything worked great.
Upgrading from a four-year old installation to a current installation with no problem was impressive. For everyone who contributed to making the magic happen, thank-you!