Users of stainless steel tanks don't make that mistake. But the tops of SS tanks don't fit tightly, and if one doesn't hold it correctly when inverting... the result is worse than forgetting that plastic tube.
Mark Overton
Maybe you don't make that mistake but that just gives you the opportunity to make all sorts of other great mistakes!
I have steel tanks too. When it's really important, I put a lap of electrical tape around the top. That leaves me more time for my favorite mistake. When I get distracted talking to somebody and I forget whether I just agitated my film at the top of the last minute or if I'm just about to agitate at the top of the next minute.
Yes, I know, it should be a trivial thing to remember but I've got a touch of A.D.D. and every once in a while... Ooh, shiny!
I just have to expend a little more effort to keep my mind on my work than most people do. The trick I use to prevent that is to set my tank down in a different corner of the sink each time.
Start off setting it down in the top-left corner of the sink. On the each successive round, put it in the top-right, bottom-right, bottom-left, etc.
I might make myself seem like a retard when I explain it but this is what I have to do in order to prevent mistakes.
Using a digital, countdown timer that beeps when it's done also helps keep my mind focused.