Don't try to do too much. 36 offers in one trip is excessive. I make multiple trips in a week. The advantage is many of the rebates return after 24-48 hours, so you can concentrate on those items you really want.
and you have a better chance of finding the items. I went early Sunday before the stores were too crowded and couldn't find several of the items that I wanted so I didn't complete the Make it Rein bonus.