Currently I'm using the EC stack just for workout energy so I only take the stack once, right before my workout. I should mention that I find I need to take it a solid 30 minutes before my workout otherwise it peaks in stimulation after my workout. It seems to hold its effectiveness as a stimulant for well over 2 hours.
No, I don't have asthma. As far as side effects, the only one that jumps out at me is that it can tend to make me irritable but this seems to subside after I've taken the stack a few times and I've become accustomed to its effects. Depending on how sensitive you are to stimulants, it might be a wise idea to start with 200mg of caffeine and just the 12.5mg of Vasopro.
I have yet to use it for cutting purposes so have yet to use it more than twice in a day. Personally, I'm pretty caffeine tolerant but don't think I could handle taking it every 4 hours. Like I said, start with a low dosage and evaluate things from there. Just be wise and use in moderation.