I will be posting all answers to questions that Almine felt would be of general interest for students. I've mentioned this a few other times but Ana, Marc and Kelly have posted prior to my getting this done - I'll manage to get them up here within the next few days. (I have time-sensitive projects due to upcoming courses.)
It's wonderful there is such an open forum to share this information. So, coming soon...more answers!
Blessings,
Jan
YOGA: typo correction to Ana's posting of her answer
Answer: The yogas have different purposes. If there is a need in your life for a very specific purpose such as overcoming old programs you would choose Shrihat or you need more resources- you would choose Irash and you would focus on that one particularly.
If the purpose is for the benefits that the yogas bring and there is not a specific need that is prominent then I would recommend alternating them.