Damois putting health aside for this discussion and assuming all things are on point, you simply will only grow to a certain amount when taking x amount of a compound consistently forever. Example, if you take 750mg Deca for a year and 1g of test, will eventually plateau (reach the limit of how big you can get on that dose). To get over that, you simply have to up the dose. Now, I firmly believe people are impatient and simply want to see results so they keep adding compounds or increase the dose too early, I don't agree with this; though I even have been guilty of this in the past. Deca in particular takes time. I'd also say anyting below 600mg for a healthy person is a waste of time. 1g Test, 600g Deca, run for 5 months, monitor ones progress, make sure they eat in the process, do light/moderate cardio as well. If at that point one stops growing, up everything 400mg (personally I do not ever go over 2g of Deca max, and try to keep 1.5:1 or 2:1 ratio of Test to Deca, just because that is what works for me and keeps my sex drive up). Individuals change compounds for various reasons. Some respond better to some then others. Tren is a decent drug and can give one a harder look then deca, but in excess (over a gram I find it's better for cutting, plus it comes with a lot of side effects). Granted, for a first cycle, only Test should be used, period