I've still been working through the old Harper's puzzles. I've gotten up to, but haven't yet printed out the puzzle for, my birth month of June 1979. I had to skip one or two because their pages weren't scanned as part of the online archives,1 so that's around forty puzzles in a little over four months.
They've been a pretty good mix of difficulties: though the easiest ones feel considerably easier than contemporary puzzles ever seem to get, there have been a couple that have taken me a while to crack.
1 Extra frustrating, because those must be the ones that are so fun that somebody just had to rip the thing out of the Official Harper's Archive Copy before it could be scanned. Ah well.