I remember hearing before that the reason we don’t need to tovel 9x13s is because it is a one-time use. I don’t work in the kitchen a lot, but I recently realized that my mother started a new thing: when it looks like the pan can still be reused she would rinse it off and use it again, until it needs to be thrown out. I don’t want to be disrespectful and ask her anything about it, but she might not be familiar with this Halacha or did I just understand the Halacha wrong? If she isn’t able to do this without toveling, what and how should I tell her respectfully?
According to a number of poskim disposable aluminum pans do not need tevila. This is because the pan is not really meant to serve the person for a long time, rather it is used very briefly, and then thrown out, and therefore, it isn’t considered a “utensil” to be obligated in tevila. According to these poskim (which is the prevalent minhag in the U.S.A.) even if it was used another time or two, it is still not enough to consider it a real “utensil”, rather a throw away item, as it isn’t meant to be used for long term. Therefore you should not say anything to your mother, as this is the minhag of many people, which is based on a number of poskim.
As a side point, there is a misunderstanding among many people that it is permitted to use a utensil once before toveling it. This is not true. A metal pot, which needs tevila may not be used even once before it is toveled.
Chelkas Yackov Y:D 46, Minchas Yitzchok 5-32. 8-69, Oz Nidberu 7-71 Igros Moshe Y:D 3-23, Nisovos Hahalacha 46 pg. 594 in the name of R’ S. Z. Auerbach zt”l, that if it used only once then it doesn’t need tevila. Also see Hiechal Horaah 1- 119 that it may even be used a few times.