Actually you can diagose the lifters without pulling it all apart.
BMW as made extensive surveys on replaced lifters, and they found that a very large percentage og the replaced lifters did not have any faults. They have a document describing this.. But unfortunally i only have it in German.
They describe typical faults and how to diagnose.
One fault is that air has come into the system, this can happen in extreme cornering, and or if the oillevel has gone too low without refilling. They have also seen failed gaskets in the oilpump suction pipe. Resulting in airpockets on the lifters. The procedure for testing for this is to use a hardwood stick and load the lifter with approx. 1kg an pushing it a couple of times.. If it feels springy its almost certain its air in thesystem. (This test needs to be performed with the valve closed / The camlobe pointing away from the lifter)
Another test you can do is to test if the valve is leaking. Ensure that the valve is closed/lobe pointing away from the lifter. Now using your hard wood stick load the lifter with approx 3-4kg for 15-20 seconds, if it's being compressed slowly during this test. The lifter is faulty and needs to be replaced.
Using a analytical and systematic approach a good mechanic can diagnose this without too much trouble.
Air getting in, does not mean you need to replace the lifter.
There is no way to install new lifters without getting air in them.
I am interested to see exactly how install is performed without compressing the lifter and it sucking air back in as soon as you start the car because as soon as the engine rotates, you are compressing and decompressing the lifter without oil pressure, with no oil near it will inevitably suck air when the cam rotates back off of the lifter.
Granted most of the air "should" bleed back out once oil pressure comes up, but there will always be some as air rises, and there is no bleed port at the top.
Even performing this test in fact can inject air into the lifter.
Lifters bleed down while sitting, what replaces that oil... air. It is normal.
And yes, lifters can go bad, they wear and bleed down too fast. This makes noise and does not fully open the valve.