Beyond 24 hours? Certainly psychological.
In the brain, the parts involved in the creation of memories are very close to those used for the smell (and therefore, for the taste which is basically the sens of smell + only 4 different sensations on the tongue). Memories and smells are therefore very connected to each other. It's probably the origin of the Madeleine de Proust.
If you think about it, you'll probably realise that you were thinking about your last sexual act before you were actually
tasting and smelling it a second time.
It's especially a strong feeling when it's about very peculiar smells or intense memories.
During my early college years we had to dissect deceased people who were treated to slow down the process of decaying. Such bodies have a very unique and strong smell.
It's been two years now, and the simple fact of thinking about it while I'm writing this post I get that smell back just like I had some decaying fat under my nails.
(
And eventhough I know it's all in my head, I'm pretty sure it's going to last until I actually wash my hands with soap... >_< )