Out for a Scroll

Sears had a bunch of different blades so I bought several different ones ( spiral, skip-reverse, etc. different TPI of each type too... ) to try out as I am getting back into scrolling. I downloaded and printed up a scroll saw blade chart (pdf) http://www2.woodcraft.com/PDF/Olson-scrollblade-chart.pdf from Olson and a "manual" from shop smith that seems to have a lot of good general info http://www.shopsmith.com/academy/scrollsaw/021003.pdf. Also bought/borrowed/downloaded a couple of books on scrolling and of plans to try out from easy to hard. There is one question that I could not find an answer for: How often do you change the blade to a new one? I know there are factors that will play into this like the wood's hardness/density, moisture content, thickness, amount of sawing that is needed to be done (the amount/area of wood you are removing), among other factors like what material you are using other than wood like corian, coin scrolling, etc. and there is also different people's personal preferences to be considered too. Personal preferences are an area that I tend to pay the most attention to since these answers come from actual experience. So, As a general rule, how often do you change the blade when you are scrolling? How often vs. what material vs. the amount of detail etc.... Thanks so much in advance.

Larry, sent you a message.

Thanks to all. I guess that I will just buy a variable speed one later. This one will have to do for now and that's ok with me, it seems to be a pretty decent machine.

I have a Delta SS 200 saw that I got for $25 and it seems to be in great condition. However I would like to have variable speed control and I was wondering if the "Router speed controller" that Harbor freight has would work with the saw. Prefer not to damage the saw motor inadvertently by doing something stupid... Thanks.