How Long Can They Last?

The TGPs that is?

My Grandfather owned a casino in Carson City Nv in the 60s and 70s. He was the custodian of a collection that has gone through 4 generations of the same family. My Uncle inherited his collection which included a mint sewn bag of 1887s'. We opened it up for the first time since it had left the mint and cherry picked an exceptional PL with great contrast and little to no obvious defects in the prime focal areas. We submitted it to the PCGS and it came back "cleaned". Up to that point my Uncle had toyed with the idea of sending his rarer coins to be slabbed. But he reasoned that if they could not tell a cleaned coin from an MS coin then it was not worth the money.

Now I have read and re-read many post from people that say they have wasted money on submitted coins that come back body bagged.

So my question is how long till the average collector gets fed up with sending money for services they don't receive?

Secondly how long after that does it become a trend? Meaning that at some point it reaches a point where only dealers send in their coins to the TGPs?

It seems to me that if it reaches a point where the average collector does not trust the grading of the TGPs, then what economic benefit will remain from having coins slabbed, even by the dealers?

Yes, I know it can be worth it to detect a counterfit coin. But other than an ultra rare coin, why invest the money?

Just curious about other opinions on the long term viability of the TGPs.