As time passes we may see fewer purge valves installed, because the original reason for their existence is slowly going away.
As introduced, all Airflow Performance fuel controls had drum mixture valves. The business plan was fuel injection for any high performance application; the drum valve is easy to machine, not fussy about fuel type, and shrugs off dirt. However, it also had a small leak rate at ICO, and didn't always shut down cleanly when the operator pulled the mixture knob. So, the purge valve dumped fuel pressure at the divider for instant shutdown. The secondary (but better known) use, circulating fuel prior to hot start, was serendipity.
In recent times AFP introduced the FM-150, a fuel control matching the physical dimensions and flanges common to a Bendix RSA5, as well as the Precision and Avstar clones. Although it's bore and venturi are quite different, it included a disk-type mixture valve like the others. And since then, AFP has been developing new valve sections for older designs (like the popular FM-200) which include a disk valve.
Here's the thing. The disk valve has a very low leak rate, so it shuts off clean in ICO unless damaged. You can still order a purge valve if you want it for circulation prior to start, but it's not standard with the disk valve fuel controls.
Best I know, there are only two potential risks to installing a purge valve. All installations should be inspected for the use of an aluminum nipple between the purge valve and the divider body (it should be stainless steel). The other is the cable and links to operate the valve. Poor hardware choices, notably breakage, may inadvertently move the valve arm in flight.