Yes, Silver Coins hiding in the ground are a finite resource. And with the increasing number of detectorists and the improvements in detector capability as per depth, multi freq etc etc, the usual places of parks, schools, playfields, fairgrounds, rodeo grounds etc will eventually be cleaned out of silver.
Your choice is to give up hope of finding silver, or look for new options where silver coins are still in the ground. I live in a town in Western Montana where I don't waste time on ANY of the above spots as I know (from trying) that a silver coin would be a very rare find at those locations.
Private yards and curb strips on the boulevards / streets are very visible AND YET STILL PRODUCTIVE places to pull silver. Research thru old maps, views of early black and white Real Photo Postcards showing abandoned rodeo grounds, ballfields, swimming holes and just about everything are great leads to chase. Talking to local old-timers as to where they hung out can be good. Was just looking at some old photo postcards on eBay the other day, some showed a baseball field, now just a pasture, near Circle Montana. Another read in a history book of Western North Dakota mentioned an old county fairgrounds, now on "so and so's private property" that operated from 1909 to 1920. You bet I will chase those leads like that, and the silver coins will be there!
) I would say the big Mack will be 100 bucks when a copper penny is with a dollar. 
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