I've purchased two 10/20 shelters.  They both are still standing.  One of them is over five years.  Showing signs of wear but still useable.  The second is on its third year and is perfect.  The secret to the long-lasting life is all in the prep work.  Installing with direct ground contact is going to lead to problems.  Lay out the frame.  Level the ground.  Stake pressure treated 2/6 planks in place. Secure the frame with lag bolts to the frame.  On the inside use ratchet straps on each leg to the 2/6.  If the forecast is calling for wind, cross brace the interior with ratchet straps.  I live in Massachusetts.  We have all kinds of weather.  The last snowstorm gave us two feet of snow.  I had to remove the snow a few times.  Still standing.  My opinion is if your shelter didn't fail you did!