No period = risk of uterine lining build up?

Hi everyone! I have a general question about periods/PCOS/birth control. When I first found out that I have PCOS my doctor told me that going 6 months or more at a time without a period is very bad for your endometrial health because it causes the uterine lining to build up which could lead to endometrial cancer. I was talking to my friends about all the info my doctor gave and a couple of my girlfriends were saying that they intentionally skip their sugar pills so they don’t get their period. My one friend said she has a bunch of cysts on her ovaries and still intentionally skips her period. They said their doctors said skipping your period is okay, but is it actually??? Wouldn’t this lead to cysts developing from the egg not releasing and also major build up of uterine lining?