I work full time running Debian on an eee-pc that is now three years old.
All I've had to do is type this :
apt-get update && apt-get upgrade
in a console window once in a while to keep my system up-to-date.
I did the same on my previous laptop for the preceeding three years, the machine is still in use.
In the meantime, Windows' Office suite has become absolutely useless to me, due to the staggering amount of changes introduced for reasons I can't fathom.
I have no idea what potential interruption in business you talk about, it certainly is far less common in open source software than in proprietary software.
One thing is certain : I am not looking back.