Post-שבת הגדול Drasha

• On the advice of our lunch guest, I found Tzipporah's answer to Friday's question in the ערוך השולחן.  He also gives another answer:  The splitting of the Yarden, a lesser miracle, also took place on י' ניסן, and we don't want to dilute the celebration of the miracles of מצרים by adding other miracles.  It was apparently quite a day.  It's interesting that we don't find a similar concern for אבילות on Tisha B'av or י"ז תמוז, where we have many reasons for mourning, some more powerful than others.  Even at the ליל הסדר, we associate the night with other historical miracles that occurred through the generations - see ויהי בחצי הלילה.
• An anonymous student also pointed out that the Drasha by the Rabbi (= Gadol) is one of the suggested reasons for the name שבת הגדול.

• Rabbi Zev Rifkin, a local Rosh Kollel spoke about בדיקת חמץ.  He asked, no matter how good a בדיקה we do, it's not fully sufficient - are we re-examining the oven?  So he defended the current "minhag" of doing only a cursory / ceremonial search, and says that once we have spent weeks cleaning and searching for chametz, all of the rooms in our home are בחזקת בדוק, and no longer require בדיקה at all.  If so, how do we justify our ברכה?  Isn't it לבטלה?  Therefore, he said that it is appropriate to leave a small section of your home uncleaned at all  (a cabinet, a knapsack etc.), and do that during בדיקת חמץ, in addition to the charade of finding the 10 pieces of chametz that are set out.  I mean to check with other Rabbanim to see if this is a mainstream view.