I've heard adrenal fatigue/burnout can be an issue with long-term stumulant use. Not sure if that would be an issue about cycling it only 3x a week though.
I did the same thing, using it 3x a week and didn't cycle it. After about 8-9 weeks I found it didn't have quite the effect it used to. Im not sure about adrenal fatigue, but you will definitely find you need to take more and more to get the same effects.
Currently, I take it on 3 of the 4 workout days doing 5/3/1. And during my deload week, I stop taking it completely. Although I feel I should be taking more than only 1 week off, Ive found it keeps me fresh the last few months and its working quite well. It really comes down to how your own body handles it.
Eventually I may even take 2 weeks off. Wave 3 and Deload week. So essentially a 2 week on/2week off cycle.
Hope this helps.