How long should a workout be?

I think my workouts are too short, i usually have a workout for 15 min. on one part of my arm, but im not seeing much results. how short can they be because my weights are too small now so i just try to do more reps to fill in the time.

My workout is 1-2 hours and thats because I have time for it. If you want to be efficient with your working out time you could rest less and you'll have more energy to finish up quicker.

Its not what you know, its what you can do that counts!

Age: 18
Height: 5' 7"
Weight: 162 lb
Current Status: Strength Training (Max-OT)

Well it all depends what you do on your workout days. For example today i spent about an hour an a half in the gym. Most people don't like to spend that much time or they do supersets or little rest in between. I do heavy weight with 1 1/2 - 2 min between each set so somtimes i end up being in the gym longer then most guys. It kinda depends on what your going for....

http://www.discussbodybuilding.com/Critique_My_Training/forumid_25/tt.htm

take a look in here between all the differen routines people ask about, they may not be for you but you can get an idea of how long people are in the gym

A lifting workout should be 60-90 minutes max. If you go over, cortisol levels spike.(Bad, very very bad) Stay under 90 minutes of lifting, and you'll be fine. Keep resting periods to under 3 minutes, and if it's cardio, do as much as you want.

Current Supplements: Multi, Whey, Caffeine, BCAA, Vitamin C, Calcium
Current Cycle: Strength

"Do not go where the path may lead, instead go where there is no path, and leave a trail."

Well to much cardio can be bad, it can lead to muscle loss, also don't do cardio (other then warmup) before lifting because you will use your main source of energy (glucose) and instead your body will burn up muscle and fat as a source of energy.