... when you keep all that saved (on computer or in your head) to post in a thread like this one
Actually, I had a thread like this about two years ago. http://www.gamesas.com/index.php?/topic/983443-you-know-youve-played-oblivion-for-too-long-if/page__view__findpost__p__14216397
Here's some more from there:
...you look for your Daedric, Amber, Madness, Glass or other favorite Oblivion bow when Bow Hunting season begins.
...you try to cast Chameleon or Invisibility when a deer (or other animal you're hunting) looks right at you.
...you try to cast an area effect Fire Damage spell to melt the snow in your front yard.
...you look for an opened Oblivion gate because the sky is red, then realize it's due to the setting sun.
...you think you can safely swim while carrying 150 pounds of stuff.
...you can tell Viper's Bugloss from Nightshade at a distance, but you can't tell an oak from a hickory in real life.
...you go deer hunting and try to outrun them.