It's impossible to tell from pricing what APMEX's stock looks like but they are selling the easy to find '72 for more than the less easy to find '71 that is always tarnished. This suggests to me that they cull out very few sets so they'll all be typical. The '72 sets will have a few coins that are tarnished lightly and the '71 will have several or all of the coins tarnished and some that can't be saved.
I do not recommend collecting or saving mint sets. I saved the nicest 20 sets I ever ran across and when I opened my safety deposit boxes several years ago they were a fright. Fortunately I had saved some nice Gems out of the packaging and even soaked them way back in the '70's and they are all still pristine. The problem, I believe, is partly contaminants left on them and mostly PVC in the packaging. If the packaging is kept very dry and they are stored vertically they seem to do better but even the best are hazing.
I do not recommend collecting or saving mint sets. I saved the nicest 20 sets I ever ran across and when I opened my safety deposit boxes several years ago they were a fright. Fortunately I had saved some nice Gems out of the packaging and even soaked them way back in the '70's and they are all still pristine. The problem, I believe, is partly contaminants left on them and mostly PVC in the packaging. If the packaging is kept very dry and they are stored vertically they seem to do better but even the best are hazing.
Time don't fly, it bounds and leaps.