casters: if you roll it a lot. we would roll ours over a mile a day in a big plant. the company would buy commercial casters and we'd weld up an angle iron frame for the box to sit in. even those would break from a rough floor. they bought my old box because it was a wreck and i bought the one your looking at.
if your just rolling around the shop they're fine. i used mine in a smaller plant with smooth floors and have never had a problem. now it's at home.
we have a tech with one of those big 8ft long snap-on, no top box. it has six 6 inch wheels on it, takes 2 guys to roll that one. his tools are one layer with lots of ''space'', mine is jammed packed shake-the-drawer to get them closed. kids... they think the box makes the tech. he's been paying for that box for years.