Aloha ralphptf,
I believe it if referring to the first and secnd half of the Active exercise CD as being 30 minutes each
You can work with the exercises however you feel led. Once again - less is more, slower is faster.
There are a lot of ways to make a 30 minute exercise CD...
in iTunes put the exercises through joining of Yin & Yang into a playlist and when it gets to the second bell in the Joining of Yin & Yang, bring your focus back to your lower Dantain, take three deep breaths, and continue doing the Harvesting n your own (that way I add in the patting of the tail bone and hip taps at the end.
just play one of the tracks from Inner Beauty or Back to the Universe (30 min)and choose two or three of the exercises, ending with the full or abbreviated Harvesting of Qi. If the music comes to the end and you are off in the emptiness and only got to one of the exercises, great. Then just bring your focus back to the lower Dantian and do an abbreviated harvesting
mix and match two or three exercise tracks from CD5. I generally prefer to make a playlist of something like the beginning, forming, and moving of Yin & Yang tracks, some silence (to get seated), and then cue up the Small Universe, Self Concentration exercise, or whatever meditation I may be doing that session.