In reading a couple of threads it seems there is a thought that over excersing can actually cause a plateau. I feel like this may be an issue for me but wondering how you calculate the right amount to do?

Weight loss does sometimes come to a halt after beginning an exercise program and that is the time to start measuring instead of weighing. Muscles retain Water while they are repairing (after heavy workouts/weight-lifting) and that is why the scale will not reflect your true progress. Before starting a program be sure to take measurements of your neck, shoulders, both upper arms, chest, waist, hips, both upper thighs and both calves. Take follow-up measurements every month.

A few years ago I was 6 weeks into an intense weight=lifting program. My weight had 'stalled' but I persevered. I suffered a back injury and had to quit lifting entirely for a few weeks. During that time I lost 6 pounds in 10 days. Just shows you how much water I was retaining!

A good program should include weights 3x a week and cardio 3-5x a week.

I dont really do much in the weigh of strenght training, just the very very basics two or three times a week becuase I hate it.

But I find 45 minutes to an hour of cardio (running usually) five to six times a week perfect for me. I wouldnt want to do any more - because I dont think its necessary for fitness, it increases the risk of injury too much and I have other things to do.

To save time, I combine cardio and strength training. I use my treadmill for this - 2 to 3 times a week instead of going out for my run I do the following:

hop on the treadmill, walk one kilometre whilst doing fairly heavy (10lb) biceps and shoulders routine. Then I alternate running 200 metres (quite fast) with hopping off and doing 10 squats, 10 lunges each leg with a 40lb barbell, 3 times, that covers another kilometre on the treadmill, then I alternate running 200 metres with 30 tricep dips 3 times, then running 200metres and 30 pushups 3 times and then 200 metres with 30 crunches, leg raises combo 3 times. It takes about 50 minutes and is a pretty good overall workout.

That's plenty I think, anymore is just really not necessary, except if you're doing it under supervision like on The Biggest Loser.