Hi Kelli and Daniel,
how about turning your 5 Day-Challenges into free mini programmes that can be scheduled like your regular programmes? It would make it much more convenient for your regulars AND it would be a major incentive for people considering to buy a programme, as it would give them a general idea on how to use the calender, how your programmes work, etc. ...
P.S. On celebrating 5 million users - how about a 5 Day Challenge for Absolute Beginners?
(no, I'm not looking at my husband right now, you are ;-) )
All best, and have a great weekend!