Welded structurs tend to settle for a long while too because most are not stress relieved and the heating/cooling cycle for the sun rising and falling is enough to make the residual stress shift things around abit.
I had a weld table blanchard ground and it settle to a new shape after about 1year. Need to get it reground but I don't have any incentive as I don't do much welding anymore (professionaly anyway)
thanks
Michael T.
"If you don't stand for something, chances are, you'll fall for anything!"