[ngoma]

Worth replacing only if they are worn or malfunctioning.

Spray pattern should look like a fox tail straight out, not a pee stream or crooked.

I did use Monark GTD style several years ago. It ran fine, hard to tell if there was any performance or economy improvement. Minimal, if any. Had more to do with my careful lapping/testing/setting procedures that they were well balanced.

That was years ago, no telling where the Monarks are manufactured now, or what their quality is.