Debian is widely regarded and typically provides two to three years update support for a given code name (e.g. Wheezy or Jessie). There is a proposal for providing Long Term Support (LTS) for Wheezy as has been done for Squeeze.
But only 2 to 3 years? That is very short. What would be a good alternative with longer support? There must be market for it I guess. Don't companies simply want to run their stuff as long as possible? Many companies still use Windows XP. And that's 14 years old.
Any major distris that commit to 10 years of support or something?
CentOS/Scientific Linux/Springdale Linux are free clones with free updates. Oracle Linux is a free download, but not sure how updates work. Current is version 7 with support until 2024.
PS: if you are asking this kind of question here, you might want to take your local Linux sysadmin for coffee and explain your use cases, applications, hardware spec and likely traffic in detail.