"the poorer materials some manufacturers use in their fuel systems"

Paul, you have hit the nail squarely on the head.  I have a Ryobi leaf blower that sets for weeks and always starts.  I have a JD 318 that sets for months because I only use it to blow snow, if the battery is good, it starts and runs.  I have a Homelite chainsaw that sets for months and it starts and runs fine. 

There are other machines and vehicles, two 20 years old, that run fine and always have.

The only tool I have trouble with is a Stihl weed eater.  I've replaced the carburetor twice.  I have run it with Sta-Bil until it's empty and still had trouble.  The dealer blames ethanol, I blame Stihl for failing to keep up with the times and being too cheap to use quality components.  I'm basing this on the fact that the aforementioned tools and vehicles have no problems.

It's my opinion that some manufacturers find it easier to simply blame ethanol than to spend the money to equip their machines and tools with modern fuel systems.  Either that or they are very friendly with the petroleum industry and are being utilized to harm the competition from ethanol.