I keep my fusibles sealed away from the air. My interfacing is stored like fabric.

My thoughts exactly!!

I have had the glue backing start to come off the paper portion (like wonder under for example) after some time.

Every month?? That stuff ain't cheap. I have some that's probably 10 yrs old and it still seems to work.

One month? That is ridiculous. I keep my for years, works fine....they sell it in huge rolls that lasts me for years. I have had separating interfacing new from the store....all depends on storage.

Seems like if it as only good for a month it would have to have an expiration on it. It is kind of expensive to just throw away. I have some though that is a few years old & is still good but I have had some that wouldn't fuse too. I just thought I might of done something wrong when I ironed it. Maybe I left the iron on too long or something. I don't know.

I have some I bought probably 20-30 years ago. I keep it in an upper cabinet and it never gets wet.
If and when I decide to use I bet it will be fine.

i've never had a problem with any of the products

I have bought Steam a Seam that is not sticky -- the shop owner would not take it back because it was still able to be ironed on (never mind that it did not stick without ironing). Frustrating since I wanted it for the sticky property. I store my water solubles in a plastic bin to keep them dry.