How long is too long?

A few days ago, Tim sent me an e-mail about Bryan Fuller leaving "Heroes," and he asked if I would still watch. My answer was I don't know.

On one hand, "Heroes" hasn't been up to par in a while, but on the other hand, I feel like I've invested so much time and energy, I have to keep watching in case it gets good again.

The more I thought about it, I realized I have the same problem with "Lost" and "Smallville." I have watched both shows since day one and while they may not be as strong as they used to be, I have to see them through to the end.

Unfortunately, this creates a backlog on my DVR and creates more shows that I have to keep up with. So my question is, how long is too long? When is it time to give up on a show and move on.

Don't get me wrong, I have no trouble giving up on shows when they go bad, but with sci-fi and serialized programs if you miss too much you'll never be able to jump back in. So it always comes back to what happens if I stop watching and the show suddenly gets good again.

While I don't see "Heroes" suddenly turning things around, there's the tiniest bit of doubt. I guess what it really comes down to is what else is on and how much DVR space I'll need.

Maybe Tim would like to share what shows he knows he should give up on but can't because he's invested too much.