Just like other people have said; If you're not having problems, then pedal on. You'll know if you're having any sort of pressure problems down below.
Having something that you've adjusted to fit "as well as possible" usually works just fine. Tweak the fit until it's comfortable for you, (which it sounds like you've done) and you should be able to ride your self-proclaimed "piece of junk" until it falls apart underneath you. You don't have to get a fit-kit and spend $1000 to get a good, solid, dependable bike that fits well. Knowing how to make the necessary adjustments to your saddle and handlebar positioning are really the key elements to fitting a bike, as long as you have the frame size correct. The biggest difference really becomes apparent when putting massive miles on the bike. At 10 miles, you might not notice that you're a little bit forward and leaning on your bars too much (or whatever fit issue there might be.) At 30 miles, your wrists might ache a little because of it. After 100 miles, you might have some numbness or harsh pain from it.
Unless your bike is causing you pain, you're probably fitted pretty well to it.