If performance is a requirement, test for it.

Otherwise Wally can write an infinite loop and leave early "It takes a while." He can claim.

Your software acceptance test should have a detailed acceptance test for various operation performance characteristics.

If you don't do this you're not engineering any performance into the product.

The performance ( like the resource consumption ) should get budgeted out to sub-systems. Then the sub-system acceptance tests can check them.

Then you can test early and often for performance. Even unit tests can then check it.

So now developers have it as an acceptance criterion, and can organise their approach to suit it.

Where I'm working now, the performance stress test is 2x bigger than any customer data set we know of. It regularly breaks a new version of the product. Good testing.