Well supposedly the fat burning mechanism continues to work and even improves through continuous use. However the side effect quickly deminish. The side effects however are not always "bad". The energy boost that you get from the caffine for example quickly dies and its imediate energy boost (along with jitteryness) is considered a side effect. Its alot like coffee eventually the caffine just does not effect you.
Many of us use the stack for the pure energy it gives during a workout, this energy giving effects of the stack diminish as use prolongs, other side effects such as increased heartbeat also subside while this is considered good for saftey reasons, the increased heartbeat is one of the things I believe that also makes the stack so effective.
It is also easy to develop a dependency on caffine, think all of the millions of americans who cannot wake up with out their morning cup of coffee. There system is wired so that the negative feedback loop (that attempts to surpress the coffees stimuli) is engaged, they physically need the coffee just to counter this loop. Another aspect of caffine withdrawel is headaches.
I've used the stack for extended long periods of time, and when I finally decided to get off, I did crash. To be honest the crash did not last long at all. a couple days at most and my system was back to normal.
So, mabe I should have gone further into reasons to cycle, since there are definitly advantages of cycling however there are equal reasons not to cycle.
It depends on what your using the stack for.
If your taking it just before working out for energy to power through cardio or caffine stim to fire off more muscle fibers during lifting, then I would suggest not taking it on days you do not workout.
However if your taking it for the ephedra fats burning aspects only, then yes it might be better not to cycle it.
When I answered the question, I should have gone further in depth, yes 5 on 2 off is a great method, but so are many of the other methods
Personally I take it , before training only, but then again I train everyday so I myself don't have cycle off periods either
And my thoughts on the aspirin yes it works, it prolongs the effects, If I take aspirin with my stack in the I have trouble sleeping at night because I'm still slightly wired. however if I don't take it, I have no problems being tired at the right time before I want to sleep. The reason alot of people do not notice the effects of aspirin I believe is because they take the stack 3x a day, can't notice its prolonged effect when your already renewing its effect 3x a day.