Would The First Years Of Mintage Be Considered Key Dates

In general, no. More people save first and last year than other years, even by people who don't seriously collect coins. Plus, the mint often makes more of first year coins, look at the number of Susan B. Anthony or Sacagawea dollars made in the first year compared to subsequent years.

Given the number of modern coins produced, I'm not sure there are 'key dates' for circulating coins, take the lowest mintage nickel in recent history, in 2009 the mint made 86 million of them and people have saved them by the roll and by the box. They probably will get an above average price, but no where near the premium associated with a true key date. The 2009 penny is another example, a low mintage year, plus it had 4 designs. Still, hundreds of millions of each design were made. Or, the 2010 penny, a first year new design, 4 billion made, I can't see how that becomes a key date.

even non coin folk keep first and last year coins as a keepsake. More often than not they are in better conditn because of this.