Questions about a cover condition

Newby question. I don't collect covers and normally throw them out when I acquire a couple here or there. In this case I acquired a bunch of covers at auction (with other stuff I wanted), I have a store so I thought I'd try to sell these cheap. They are all from the same source (same name and address on the front). Because they are all same source, I am assuming storage is not the issue. Some of the covers have glue bleeding through. This is the factory sealed edge, not the edge that gets licked. If you know, would you folks kindly educate me as to what causes this to happen? Does it make them so undesirable that I should just throw them out. In my opinion most of these covers are borderline because of other issues anyways. They are yellowing and are showing their age around the edges. All of these covers came from Canada and are late 50's - early 60's if that makes a difference.
Comments
The things that most needs to be evaluated on the covers are franking, directional postal markings (due, forward, return to sender, dead letter office, etc) and sender/recipient. If these are unusual in any way, then the value is there in spite of the adhesive bleeds. Even certain types of machine cancellations can have value. If not, then, yeah, donate them. It would be helpful for evaluation if you showed scans of the fronts of any covers you think aren't run-of-the-mill...
George - I did forget to include they are first day covers. All of them had stiffeners inside, but through the envelopes you can see that the stiffener is just random paper and sometimes thin cardboard. I think all of them are run of the mill. They start at Scott # 360 and run to #410. I'll attach a few more random scans just for shits and grins.