What makes something worth revisiting?

I am sobbing right now.  You see, this character died suddenly and with little fanfare, and it's kind of rough.  Even though this is the fifth time I've seen the show.  In fact, this time, I started crying early, in the episode before, because I knew it was coming.

It reminds me of the way I cry earlier in The Warrior's Apprentice the more times I read it.  This is why I think I don't ever want to be involved with any prophecies of the future and stuff.  I'd be (more of) a wreck if I knew it was coming.  (Or maybe I'd get really stubborn about making a different future happen . . . :)

Anyway, all this crying and reflecting got me thinking about the topic of what gives a book good reread value (or a show/movie good re-watch value). 

Some books are harder for me to reread because of the tragedies (Mirror Dance); while the tragedies in other works are the things that make them worth revisiting.  Some comedies are great for one watch and then pointless while other funny works need to be appreciated over and over again (Hogfather).  One friend once said that he reads David Eddings' books just for the chance to hang out with the characters again, and some people reread the same mystery over and over because they love the plotting.


What is it for you?  What makes you revisit a work over and over again?  (How long do you usually wait?)  What works do you regularly revisit (and why)?