Endometrial tissue attaches to the uterine wall, so the amount that can be accumulated is limited by the surface area inside the uterus. Your body does not throw more endometrium on top of what is there if you suppress your periods, there is no where for it to attach, nor is there any need since the only purpose for it is to nourish a fertilized egg.
I posted a guide to estimating bleeding vs period volumes in one of the threads in question. There are plenty of emergency medical guides with autistic levels of detail to evidence what I am saying.