That comment doesn't make sense.I would not leave them in all the time either, because the gas will eat them away. My suggestion is to get the float level set, then remove them and install the regular plugs.
The BG/Demon stuff isn't plastic like the Holley parts. The Holley plastic will cloud and possibly fail after time. I was removing one from a borrowed carb so I could try to clean off the cloudiness--SNAP! Oh well, new ones looked much clearer!Barry Grant carbs come with sight glasses and there's no mention of having to remove them