Some of mine is yellower than others, but a few are a couple years old now. No big. It cleans up pretty easily with soap and water since you're not pulling vapor through it. And, most of the grit/color is probably on the outside. Pull from the GonG, slip it on a fork or spoon handle and throw it in the dishwasher. Would probably come out looking damned near new. Or, it is pretty cheap and you don't really need to worry about food grade because it is outside the glass - so easy to pick up a foot of new and change as often as you like. All the reasons you list are good ones for why to keep it on. IMO the best reason is to use it as a catch for your finger so you can pull the nano and GonG at same time with one hand to clear. Just roll it down a little on to itself to create a useable ledge/finger ridge.
Definitely get the GonG! I'd go with 18mm because they're more common, and there are at least a few nice glass pieces in the $30 price range that can be had from China and have 18mm F on them. Screens are always good to have on hand. If you really want to splurge, throw an extra e-pik in your cart. Those things have a way of slipping away into the tiniest places for a week or two.
Nicely put
@AhBeVapin ! $169 is a great price, too.
OH you lucky dog!! Fresh caught tuna tacos? YUMMM!!!