2. This high interest rate will only last for 9 months... so might as well take advantage of it
What makes you think that? I don't think that is correct. The Steem Power compounding is perpetual.
I read form a post by dan himself if I remember correctly... I think the interest rate changes
I am bit confused about this. There is one form of compounding that comes from the perpetual creation of 9X Steem Power for every 1 Steem that is minted. Those 9X SP are distributed proportionally to all SP holders. So your SP holdings are always increasing. I don't think it ever ceases nor changes.
Is there also another form of interest paid on SP?