Not to be a stickler, but 'reliability' means the same results coming from similar samples. if you split a sample and send one to Blackstone and another to another company, you get the same results. I'd say reliability is excellent
As far as validity goes, That's the question of whether the tests show anything useful. I don't know. All the UOAs I see seem to show that the name brand oil does an excellent job of lubrication if not pushed too far. I've learned a few things from looking at the tests.
1. Quality oils of any brand with reasonable change intervals do well.
2. Its very difficult to discern any measurable improvement with synthetic oils and regular just by reading the UOA.
3. Fiddling with the viscosity within reason doesn't seem to make much difference.
So, I've kind of lost interest in the subject. I've turned my attention to other maintenance issues and resolved to be punctual about oil changes with quality oil and careful about monitoring oil consumption, but not to obsess over it. Last week I had my oil changed at about the 6K mark after 9 months. I would have waited longer, but its going to be difficult to get around to it in time otherwise. I had the differential oil changed instead. That's probably overkill too, but I don't know that its overkill the way it is with oil. I'll probably order up another UOA at about 70K miles to see how things are going, but that's about it.
I don't subscribe to the belief that you are likely to spot an impending engine failure with a UOA that you wouldn't better detect through other means.