iPod Touch 4, iPhone 3G/S, iPad 2/3 Adhesive. Not sticking properly.

I have owned my own iDevice repair business now for 2 years and one thing I have not been happy with is the reliability of the 3M adhesive that typically comes with any glass repair.

One thing I strive to do is make sure I am returning the product to the customer as if Apple them selves just did the repair, but with a cheaper cost and faster time.

Something I have noticed lately is that the iPod touch 4 glass doesn't come off super easy even with some heat. Once the glass if off and all the glass shards are cleared out and dusted I always install new 3M adhesive. On occasion that something goes defective with the part, and the customer comes back I always notice that it comes apart SUPER easy even with out heat, and is much more dusty inside then it should.

I always worry about doing repairs for customers and the screen falling off and then getting a bad name or reputation.

And now for my question:

A. Is the 3M adhesive the same, OEM adhesive that apple uses?(if yes what am I doing wrong since it's not holding like it should)

B. If 3M is not OEM. Where can I buy OEM adhesive whether it is pre-cut to fit, or manually has to be cut?

I have also had this problem with the 3G/3GS series and Pad 2 on occasion.

Thanks for any information!

P.S. Sorry for the long comment.