I had a nice idea for a discussion in your kollel in Shabbos, daf 18a, it says Rav Shimon ben Gamliel's father was machmir like bais Shamai (check Rashi, kli lavan.) Whereas in Maseches Brochos, daf 10b, (bottom), it says "asisi kibais shamai, vi'sikanti es atsmi mipnai halistim", so you see one is not allowed to be machmir like bais Shamai. IN addition, it also say in Brochos 11a, (bottom) R' Nachman ben Yitschok says that one who does like bais Shamai is chayav misah. ?
So far, I have come across several angles to attack this question. One is the tosfos in Yevamos (14a) "lav asu kibais shamai", which answers to a similar question that one was before the bas kol while the other was after. We find the same answer in Brochos 51b bottom.
One can figure out if this answer would apply to our question as well by figuring out who lived in whose generation by checking Maseches Shabbos 15a on the bottom.
Another angle is that we don't poskin according to a bas kol (Brochos 52a top).
Another angle is that this issur of being machmir like bais Shamai might only apply by a kum va'aseh as in the gemara in Brochos where he lied down to say krias shema. On the other hand, in our gemara, it is a shev vi'al taaseh, where he is NOT sending clothing to cleaners, it would be mutar to be machmir like bais Shamai.
Thank you for your very helpful e-mails. I have enjoyed using them and I share it with my friends as well. Tizko limitzvos!
Yehoash Orange
Brooklyn NY
A nice point, which in fact is raised by the commentaries on the Mishnah.
You cannot base your answer on 'Bas- Kol', since, as Tosfos 52a points out, that argument only holds water in the Machlokes between Rebbi Eliezer and the Chachamim, where the Bas-Kol clashed with Rov (the majority). But where we have Rov, the Bas-Kol is superfluous. And apart from the eighteen cases discussed in the first Perek of Shabbos, Beis Hillel always had a majority.
Granted, Rebbi Yehoshua holds that the Halachah is not like the Bas-Kol even when Beis Hillel argue with Beis Shamai, because Beis Shamai were sharper (and sharper possibly overrides Rov). However, we do not hold like Rebbi Yehoshua in this regard.
Your last answer however, conforms with that of the Tosfos Yom-Tov. The Bo'az puts it more succinctly, when he says that for all we know, they would hand in their laundry three days before. They did so because they wanted it back early (and not to avoid Chilul Shabbos).
Both commentaries cite the Mishnah in B'rachos Perek 8, Mishnah 7, where someone went back to the place where he had eaten in order to Bensch, and (not only was he not eaten by a lion for doing like Beis Shamai, but) he found a purse-full of gold - even though he acted with 'Kum va'Asei'.
The Rosh answers that this was because Beis Hillel also agreed that it is better to return and Bensch where he ate, only that he was not obligated to. And the same, says the Tiferes Yisrael, will apply to the case of the laundry. There too, Beis Hillel will agree that it is preferable to hand in one's laundry earlier, only that one is not obligated to do so.