Just like the law of gravity explains all the ways possible it might not work? Oh, but it doesn't do that, does it?
Your analogy is extremely unsound--so much so as to strike at the heart of your miscomprehension. The law of gravity is not being offered up as a comprensive attempt to falsify some other theory. It is a theory, derived from induction over a limited set of data, just as are all natural science theories. The reason your experiment's results are laughable, is that you have undertaken to demonstrate, however much you wiggle on the hook, that NO OTHER EXPLANATION CAN EXIST to explain your experiment's failure, for your experiment to mean what you want it to mean. The more partial view--that your test would be "just an indication" or just a slight weight on the falsification scale, makes it 1) permanently unaffordable, and 2) just plain wrong, since we have some positive evidence that said failure could be more sensibly chalked up to lack of labs with infinite time and resources, and we always first look at obvious explanations before wracking ourselves up over far-fetched explanations.
To the contrary, someone must falsify my assertion by showing at least one other possible way life can come into existence without intelligent guidance.
Done and done. See Woese.
"The contention that life takes too long to happen, for it to happen in a lab, is, of course, the most natural and obvious, and least hair-brained, of the many contentions that might be falsified by your test"
Then you should welcome my test as a way to show your assertion is falsifiable.
It will show nothing, it will mean nothing. It is test of spontaneous abiogenesis, which is creationist comic book science, not real science.
But then again, maybe you would like your assertion to be falsifiable without actually being tested.
It is tested in the same manner as assertions about the behavior or morphology of dinosaurs are tested. By digging up new evidence that will either confirm or repudiate the thesis in question.
Because, realistically, it will be falsified at some point.
Of course it will not. Any more than the evidence for dinosaurs will be suddenly ripped asunder.