My longest was when i went 100% Full time on my main machine (no dual boot), I stopped distro-hoppping. I Installed Debian stable when it first came out (Jessie) and stayed with it until it shifted to "old-stable" which was a little bit over 3 years.
A lot of people give Debian stable a hard time but i found it worked well. Most software that i needed to be a little bit newer i could get from the backports repository. It was only at the end of it's lifecycle that i noticed started running in to software being a little to old for what i wanted to do. Then i went back to distro-hopping for a while until i found my next home. :-)
Here in New Zealand you can buy it at the Hardware store in 20KG bags. Older houses have pot belly "stoves" for heat, which are smaller then log burners usually, and coal is the best fuel for them.