me I am a gym rat and do about 50 minutes of cardio each time.
I am also a certified trainer, a cscs, and teach spin classes 3 times a week at my gym. I have about 10-30 students in each class on a regular basis and I have them spin for 50 minutes with a 10 minute cool down time.
my favorite cardio machines right now are the cybex arc trainer and the precor 100i and elliptical.
If I was rich one day I would open the ultimate gym at least 30,000 sguare feet of the best equipment and class space money could buy. I would make a gym that the members love and update the equipment on a regular basis not buy something and let it sit for years like many gyms do.