Floats

Sean, welcome to aviation.  For the most part it is obvious, lawn mower people dont get sued when their mower fails and crashes.  In US law there is a sub group that specializes in aircraft lawsuits.  it is so lucrative that the FAA even requires an FAA approved repair station to carry at least 3 million in liability coverage.  (last time I checked, might be more now) They sue the OEM who made it, the person to made it if a kit.  They sue the mechanic who worked on it, if he has assets.  So yes I agree they are expensive but they take a risk.  

As for why they absorb fuel in the first place.  Simple answer, they were bad floats.  It may take hundreds of hours to absorb fuel, years perhaps.  We had almost no float failures for decades but as the world switched to injection the production of floats for small runs, like Bing carbs, dropped to extreme low numbers.  Suppliers stopped making them and new ones were not perhaps as good at quality as perhaps they could have been with the lower numbers.  

The current Rotax float is not from Bing, it is special for the Rotax engine in that they found a supplier that tested better and switched to that for QA reasons.  

I know some of you are sceptical so look up NBR floats on the internet, (that is the material) you can get an education on what that is and see suppliers of floats.  The failure of floats, for the most part, it from the original forming of them and curing.  It is not ethanol as many will try to suggest.  Have an open mind and check it out.  Obviously these are my opinions.

Cheers