Wel, SFG, here's the way I see it. I work on cars a lot...whenever I can, anyway. It's a hobby of mine. I've also spent a lot of years troubleshooting computer hardware and software. So I've done a little bit of problem analysis and correction. In a way, the body is similar to a car...or at least I see it that way. It takes in air and fuel and voids exhaust....and there are various systems that are somewhat analogous in the two systems.
But I'm not just tryin to draw an parallel between the two. I'm tryin to view an approach to problem identification and resolution. I can look at a given system and generally make an assessment about its operation...be it a computer, a car or my own body. Not always 100 percent accurate, and the body's about a bazillion times more complex than a car. However, if I'm concerned about a particular portion of either system's operation, I can make certain observations. Some are easy: check the oil, take the blood pressure. Some are more difficult: tear the motor down to see if the bearings are worn; do an angiogram to see if the arteries are diseased.
In either case, it makes more sense to do the simple tests first. Check the oil, look at the exhaust, listen to the motor runing, take it for a test drive....I'm sure you can see parallels in testing the body. Now if any of these tests show abnormalities (blue smoke in the exhaust, a knocking in the motor, leaks or drips somewhere...) then it's time to look into that area a little further. If the coolant is leaking from a hose, I'm sure not gonna tear down the motor. And if all the simple tests seem to be normal, then I sure wouldn't jump in and start tearing things apart. There's a saying, "if it ain't broke, don't fix it." Of course there are all sorts of corollaries to this, such as the racer's adage: "if it ain't broke, then break it and then make it better." But that ain't what we're tryin to do here.
Same holds true with the practice of medicine. Check the vital signs. Then ask about symptoms. Then maybe a blood test or EKG. If the tests show an abnormality, then it indicates where to examine more closely. However, if there are no symptoms and the vital signs look acceptable, there's no reason for further testing.
And it's not just the cost of the tests. I'll give you an example. The angiogram. In my opinion, this is the one way to see how the blood flows around the heart and detect coronary artery problems. But there are some problems with "just doing it." First, it's invasive. That is, the procedure involves invading the body with a foreign object (a catheter and a contrast medium, etc.) Invasive testing is usually not done until all the non-invasive tests have been exhausted...or if the symptoms are such that it seems to be an immediate necessity. Another thing about doing an angiogram is that every time it's done it builds up some scar tissue around the area where the catheter is inserted. The doctor had a hell of a time getting the catheter into my femoral artery the last time I had this procedure done. And that's only the 4th time I've had the procedure. So I wouldn't wanna have this done every year just to check things out. I'd run out of places that they could stick the cath. And maybe one time an artery would burst during the testing (it does happen) and "goodbye, Charlie."
So there are reasons that we can't always go in and have things checked at the most granular level...whether it's a car or a human body.
Now from what you've stated, all of your tests have shown normal results. In a case like this, most doctors won't do invasive testing based solely on family history. If I were to have invasive testing for all the maladies that my family members have experienced, I'd be chopped up into little bits and examined under a microscope. I'm not saying this to ridicule you, but rather to illustrate that my father and aunt suffered from Alzheimer's disease before their death. And the only way to positively diagnose Alzheimer's (that I know of) is to do an autopsy. I'm not quite ready for that.
Once again, I'm not a doctor, so I'm not qualified to give advise on issues such as this. But I can tell you what I'd do if I were in your position. I'd keep an eye open for symptoms, check my BP regularly, have annual checkups and ask to have the cholesterol level looked at, try to eat a relatively healthy diet, get some exercise and most important of all, enjoy life. If any of the tests or symptoms start to indicate an abnormality, then further testing can be done to find the cause.
That's my nickle's worth....for whatever that's worth. :)