It's not meant to be a job, just a hobby. ;) Though you can make it a job, especially in the past. There is a article out about a gentleman that was a vietnam veteran. He couldn't work anymore due to PTSD but found out about this. He ended up making a giant business out of it and make over 100k from it in a few years. You just have to go big. Of course, as the years move on things get harder and harder. It's still very good though.
If you wanted to get technical though I'm holding my silver for 10+ years. It will be significantly higher by then. I literally drive around town for 1-1.5 hours, get around 500 dollars worth of change and end up with 2-3 silver coins on average. Since I can sell the 90% for 12 bucks on each and the 40% for 6, We are talking 20-30 bucks an hour, it can be much much more on a good day. You just can't do it every day ;) There isn't enough halves brought in unless you order boxes from the armor car companies through your bank.