Trip,
The frequency change thing leads back to ATCO's spending time on flight decks, I've spent many happy hours up front and because of this I know when you're busy, the post departure clean up and checks is one of the busiest times "in the office" so you'l find that I never bother with the frew change until you're around 2000' (SID Level 6000').
You could always take the time out to visit the tower, have a coffee (and maybe a chocolate biscuit) and discuss things with the controllers
