Was checking my inflatables this weekend as part of the off-season maintenance, and although the makers recommend replacing cartridges and dissolving "pill" annually I don't see the need. The cartridges are stamped with how many grams they should weigh when full, so they can be checked with a small gram scale, or a postage scale (converted from ounces). The pills can be visually inspected.

I have one cartridge that appears rusty but weighs enough. I figure the rust is on the outside, and doesn't involve the threads so it's still good. I'll wire-brush it, weigh again, and coat with CRC or similar. Am I being unwise to rely on my own inspections?