I'm running Ubuntu 10.04. A search for "linux-headers" in Synaptic Package Manager, and selecting the package "linux-headers-2.6.32-26-generic" displays the following notes for this package: "Canonical provides critical updates for linux-headers-2.6.32-26-generic until October 2011."
Now, selecting "linux-headers-2.6.32-21-generic" displays the following notes: "Canonical provides critical updates for linux-headers-2.6.32-21-generic until April 2015."
Note that the earlier version (linux-headers-2.6.32-21-generic) is supported till 2015, while the later version (linux-headers-2.6.32-26-generic) is only supported till 2011. Why is this the case? Shouldn't a later version be supported till a later time?