I don't think it's worth the upgrade. Overclockin is quite more expensive and it doesn't make sense to do it just in order for the chip to "last longer"...
You should just keep your current chip until there is a real reason to upgrade, and at that time you can get what you want. That way you will ACTUALLY be making your CURRENT chip last longer with no performance hit.
At the moment, for gaming, there is no performance difference among those chips, and if there exists a difference (in rare cases), it would be smaller than 5%...