Time Flies When You're Debugging Contrib
Today I saw a ridiculous job posting with a prerequisite of 10 years Drupal experience. This is ridiculous because practically no one has 10 years Drupal experience. Then I checked the Drupal release history and came to find out that I have roughly 10 years Drupal experience, which is ridiculous.
Take it from me, a guy with roughly 10 years Drupal experience, if you're looking to hire a Drupal dev, 3 to 5 years of recent Drupal experience is all they should really need to be Drupal-ready. Drupal changes so much between major releases that my Drupal 4.5 skills are almost entirely irrelevant to my Drupal 6 skills, which are almost entirely irrelevant to what you need to know for Drupal 8.
Incidentally, there's no such thing as a freelance senior developer either. The very notion is a contradiction in terms.