A PCT is used to manage the transition from being on a cycle (which would typically be far more aggressive than a testosterone replacement therapy (TRT) program) to being off a cycle and back to your normal daily life.
With testosterone replacement therapy (TRT), you are not doing "cycle's". Instead of a super aggressive regimen for a short period of time, you are using a sustainable program which stays the same every day/week/year unless it becomes necessary to make adjustments.
So, the obvious answer would be that you don't need "post cycle therapy" if you aren't going to experience a "post cycle" period at all.
To be clear, though, testosterone replacement therapy (TRT) will definitely change the way your body produces and regulates hormones. If you were to stop testosterone replacement therapy (TRT) at some point, it is my understanding that you may need something like a PCT to carefully get your body back on track.
Exactly what happens when you're on testosterone replacement therapy (TRT) for a long time, and what permanent changes may take place even if you stop, is a subject that I know far too little about. It's the #1 thing that I need to know more about before I would commit to it. I'm just paranoid about never being able to produce even 300ng/dl naturally again, just in case.