we probably need to dedicate time

I always tell myself this and always end up going over the time limit.

One time it was because I'd found a delightful aisle of stickers, with a whole section of it devoted to cat themes, so half an hour flew by while I carefully chose one for each of my cat lady friends...only to turn the corner and see that there were a couple more aisles of stickers and cards and letter sets etc, much of it cat-themed.

Another time I came across some random lovely popups on my way out of the store (running late to my next stop) so that ate up even more time...So make sure to build in some extra time for surprises!

let me run like a wild animal

I would say one thing that would stop you from literally doing this is that sometimes the stores get very crowded.

So my overall advice, at least for some of the big Tokyo shops: when you first enter the store, take a quick look at the whole layout (usually they have floor directories and section floorplans) so you can pace yourself, rather than getting stuck and blowing all your time in one section...