There is no way to quantify the diminishing silver returns, but I have to think that the level of CRHing culls exceeds the amount of silver coins added to the circulating population by collection dumps. That is, new silver may be added to circulation, but the number culled in a given period exceeds the number added by collection/sock drawer dumps. I can't prove that, it's just a hunch. So, some CRHer may find those newly added coins, but they will be fewer and farther between. Logically the CRHing would exhaust the wild silver over time, but there will always be some amount of dumped silver added to circulation, so silver that's out there won't go to zero. I suppose there are people hoarding silver today that may pass away and leave it to a clueless heir who dumps it in the bank, but I'd guess that most of the time the heir will be aware of what he/she has (probably because the hoarder told them or left notes indicated the coins were silver).
From what I have seen in my own extended family and on community online bulletin boards, a common first reaction to inheriting or coming across a coin stash, even if it's just a pile of coins in a cigar box, is to overestimate their value rather than treat them as common change. With the internet it's easy to quickly determine whether you found something of value. An example is one woman I know, who had no previous knowledge of coins, who did research on the internet just because she found a tin of indian head cents in her grandmother's things. She found out that she had at least one key date and, even though she learned that most of the cents weren't that valuable, she's looking to sell them to a dealer or collector rather than dump them. She also found some silver in the stash, including old silver dollars. She was disappointed to hear from me that the particular silver coins she had wouldn't bring much more than melt value if she sold them. Some people may spend of deposit collections, but I think most people like to think they've hit the jackpot.
