I can't speak as to how long these may or may not last, but don't expect these to simply snap together.  I stacked them -- two high.  This requires plastic clips (enclosed) to hold the two sets together.  Very disappointed in the lack of tolerance for the least unlevel surface.  Clips go flying off, if you can even get them on -- I am talking about having to sit on narrow sides and try hammering on "plastic" clips.  My patio (where I thought was the most level - was still not level enough for easy assembly. Secondly, they do not mesh well when stacking one on the other. I worked for hours trying to get rid of daylight gaps and still am not comfortable that they are stacked correctly.   I do not look forward to all the leveling I am going to have to do in my garden space just to insure clips stay and the beds don't fall apart.  If you are thinking about stacking these -- you will despise Lifetime. To Lifetime I say -- You can do better.