I'm a huge fan of long workouts. An hour run, a 90-minute bike ride, or a three-hour snowshoe walk in the woods are a few of my faves. There's something about moving your body for an extended period of time that feels so gratifying. You don't want to overdo it though, and you definitely don't want to compromise your form just for the sake of saying you worked out for a certain amount of time. When it comes to exercise, think of quality — not quantity. Pushing yourself to run a 10K is commendable, but not if you end up with blisters, shin splints, and are too sore to work out for the next week.
Whatever you do, you want to be able to move with strength, energy, and control. This goes for weights in strength training as well as distances in running. Remember that a workout doesn't have to be long in order for it to be good.