The single most useful thing to understand when buying any foam footwear, and it is almost never on a spec sheet.

Compression set

EVA does not simply squash and spring back forever. Under repeated load it takes a permanent set: some of the compression stops recovering, and the footbed gets permanently thinner and harder.

How fast depends far more on density than on how thick it started. A low-density foam compresses further and sets sooner.

Why thick and soft feels best in the sample box

A thick low-density footbed is the most comfortable thing in any sample set, and that is exactly the trap. It is comfortable because it compresses easily, which is the same property that makes it flatten.

A denser footbed feels firmer on day one and is still the same shape in month six.

Layering solves the trade-off

One foam has to be either dense or soft. Two layers do not: a dense base layer holds the shape while a softer top layer sits against the foot.

That is why a layered sole is worth specifying for anything that gets worn daily, and unnecessary for a one-day giveaway.

What to ask for

Ask for the density of the footbed and whether the sole is single or layered, and get both on the quote. Then judge the samples knowing that the softest one is not the one that will last.

For a giveaway, a single-density sole is honestly fine. For guest use over a week or staff use over a season, it is not.