In my opinion like all other steroids it's fine to take deca/tren etc, as long as you take measures to remove the bad side effects that are caused by them
It's common knowledge that you SHOULD take an AI when on testosterone, since practically all the side effects are caused by the relatively enormous increase in estrogen, but somehow it's escaped everyone that the same goes for steroids that end up as progesterone and therefore increases your prolactin levels(WHICH IS FUCKING BAD FOR A MAN)
So you SHOULD be taking a dopamine agonist(cabergoline) to combat the increase in prolactin, since prolactin is basicly very very bad for a man. Ofcourse if you don't experience any sideeffects you are lucky and then you can just drop the ancilliaries, but as a rule of thumb you should always be on the safe side, since there are some permanent side effects that can occur with high estrogen and high prolactin levels. Note permanent infertility(prolactin),gyno(estrogen) etc.
Prolactin in men is mostly produced when you cum, to make you calm down and lose your hardon(the refraction period) and in extreme cases/levels makes you lactate and produce breast tissue(the so called progesterone gyno, which should be called prolactin gyno). As you can see the infamous decadick is actually caused by prolactin levels being higher than usual making the body think it isn't ready for sex again, and if you have very high prolactin levels for a long time you might end up being left with permanent erectile dysfunction or permanent infertility.
In short: prolactin is BAD BAD BAD BAD!!! there for kids, use a dopamine agonist if you get side effects from deca/tren etc.