This is my opinion and think it may be heads up for others on PCa and your future with it. Ok you got a doc, maybe a uro-doc and he says I will see you in 3 months or whatever (wonderful). Now do you only take his opinion (cause that is what it boils down to and they are not Gods and not 100% accurate and many times 'dead wrong'-sometimes sued for malpractice or even should be....sorry this is the real world....Marcus Welby M.D. is your fantasy land).
Like post surgery ok you are doing fine, forget about the small increases and see me in 3-4 months (b.s.-I say). Find another source in between and get psa tests or whatever tests you believe are in your best interests (free or paid for-who cares your life is in the balance). It may not tell you everything, but then again it could or could be watershed for your psa trend-velocity or changes and verfiying his lab results, etc. I say maybe trust your doc, always consider verifying and even verifying his words of wisdom or drug choices, whatever. You don't have to of course, but it is possible you could do better or have better care, more choices, more freedom, etc. Kind of like being put under and getting a limb removed (you are not there to verfiy and point out which one it is), you know the stories...the wrong limb is removed and these are top surgeons (fyi)....no malpractice???? Again this stuff happens, just to show how insane the medical world actually can be, sure it is rare, would you like to be done 'rare-medium-well done'???? Looking back we probably would like to say yes it all was well done, no monday morning quarterbacks.
Well you can choose to be proactive in your own case or go with the experts whom are always working day and night on only your case (sarcasm included).
Also second opinions are worth your time, I got about 7 of them....very happy I did.