How to decide when enough is enough

One of the problems i am having is knowing when to chop and edit.If a bit of film is 15 minutes long how do you judge what to keep or chop out.How long do you keep on a scene.I know it is a case of individual tastes and subjects but is there a rule of thumb.
Some of the most interesting films are the shortest with lots of bits in to keep you interested.
Thanks

Gut instinct It all depends on so many differnet things, the subject, what pace you want, for example landscape pan shot could be quite long, a car chase only seconds with differnet cut shots to imply action.

Music is a good bench mark. If you choose the music which best describes the feel of the scene the music will have its own tempo which will influence the edit.

Music helps (John beat me to it )

Get someone else to watch it. A 2nd person can tell you when they feel like something is dragging on. After you've watched it the 100 times it takes to edit it, you are pretty numb, so fresh eyes help.

BrickR wrote in post #15976962
Get someone else to watch it. A 2nd person can tell you when they feel like something is dragging on. After you've watched it the 100 times it takes to edit it, you are pretty numb, so fresh eyes help.

Or even walk away for a couple days. You come back, and go, "Why did I do THAT?!'.

Thanks for the advice ,i will carry on hacking LOL.