I'm buidling a shelf storage unit for the garage and am going to put
it on wheels to make it easy to move for cleaning or any other reason
I may need to move it.

Since this is going to be sitting in place on concrete for long
periods without moving, I plan on using steel casters since I assume
rubber casters wouldn't be a good choice that they would develop a
flat spot over time, correct?
I wonder if these hard plastic casters I see could develop problems
with potntially a fair amound of weight sitting on them for extended
periods.

Thoughts? Input?

Thanks