Some logos do have a sell by date. Some stay (relatively) unchanged for years. (See the Pepsi/Coca-Cola image below - slightly disingenuous as the Coca-Cola logo has almost certainly been 'tweaked' many times through the years).

Some logos look like they've never changed. Another designer once told me he worked on the redesign of the Mars bar wrapper and the Mars logo had been changed many times over the years without anyone noticing. A gentle evolution to stop it becoming outdated. Without this process a 'revolutionary' re-design would eventually become necessary causing howls of discontent and shock at something happening in one leap. That redesign had been done by stealth.

Some logos even need to be designed to work in the future. The London 2012 logo took a lot of stick when first unveiled in 2007, but by the time 2012 came around, it was perfect. But that logo never needed to be timeless. It was very much 'now'.