For sure ... a new blade is a must when you start cutting the 6 layers for OBW.
As another note ... some blades are not as good as others, and you m ay need to change it more often. Also, if you run into your ruler or pins or other things ... that can ruin a blade and it may only last a few minutes.
Time installed really tells nothing ... some cut more in a day than others cut in six months!
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When you get your OBW pattern/book, you will see that it describes very well how to pin the layers to be sure that they line up pefectly.
You want to make sure that they do, or else when you do your kaleidos ... well, they won't be kaleidos!
In the meantime get yourself some "flower pins" ... they are longer and coarser than you use for most sewing, and have a flat head (that's like a flower!). Once they are pinned thru the layers, they lay flat, so that you can put your ruler over, and cut thru.
Patience .... and a steady hand and you will discover that cutting the layers is not really all that hard.
If you're worried about cutting the six layers ... practice on some other fabric first, just to help you get the feel of it.