It's really not expensive, not for what you get. If you have other children coming up, then all you need to do is get a student book for the youngers. We really feel it's been a very cost effective program for us, as we've had three kids use it all the way up.
Yes, you work with your child's attention span, 15-20 minutes per day until mastery is achieved, whether this is three days or two months. :-) My typical process looks like this: (of course mine are older now, but I do remember the younger years!) First day, watch the video together and maybe do some practice problems with the blocks; day two to however many, continue doing practice problems with the blocks until the child can teach it back to me. Then I decide how many worksheets are necessary, and we work on those for a few days. (I often did one to two sheets on the new topic, then moved on to the systematic review--if they didn't miss any on the first systematic review, then I let them just do the word problems on the next two pages.) If they need some memory work on the basic facts, sometimes we'd spend a day or however many needed on the online practice on the MUS site. After this, then the test would just be a simple "See, I can do it!" demonstration, and time to move on to another topic. All children move at different paces, and sometimes the same child will do a lesson very quickly and then take much longer on a later one. It just depends. Follow your child's cues about when to move on.