I'd like to ask the ones who finished the Main Quest and are using many (or not-that-many) mods something.

Did you, after finishing the MQ, still have the desire to finish all the other mods' quests and other guilds? In other words, did you still wanted to play more Oblivion after finishing the MQ?

I've only finished the main quest once. I stopped playing that character immediately afterward. At the time there were no quest mods so playing a quest mod wasn't an option with that character.

For me, I guess it would depend on the character and the story I was telling with that character. I can picture playing modded quests after the main quest if it was appropriate for my character. I've been thinking of doing the main quest a second time with a Paladin-esque character in order to do Reclaiming Sancre Tor, for instance.

I could also picture a character traveling to a different worldspace, like Windfall or Anequina, after doing the main quest. I would see it as a kind of Lone Ranger scenario: "My work here is done." *rides off into the sunset*

Mostly, I think it would just depend on the character.