Thank You. Yay or Nay?

We've all officially survived another

"Staff Appreciation/Administrative Professionals Day/Week."

So, now here's the question for "Emily Post."  

If you happened to be fortunate enough to receive an individual gift from your attorney(s), beyond the hot dog lunches, ice cream bars, chair massages and "group company gifts,"  should you give her a formal handwritten "thank you," or is an email enough?

I'm not completely ill-mannered.  I know that bouquet of flowers or that box of candy or Starbucks gift card deserves a phone call (make it quick, it's their billable time) or an email.  But, should you take it even further and write out an old-fashioned "Thank you?"

And does the "one month after the gift, thank you card" rule apply to Secretary's Day?  

If not, I'll gladly take your answers to apply to next year.