Being in the auto/truck glass biz I've found the LocTite brand consumer packages of rear view mirror adhesives to be about the best out there----its what the OEM glass manufacturers use during production. Other brand names including Permatex just don't seem to be as long lasting. That's odd because Permatex and LocTite are essentially the same company.
Try finding the actual LocTite brand regardless what the local sellers try steering you towards. perhaps online is the best source for those not in the glass biz.
The key is using a bit more than one might suspect in order to build a thicker pad of adhesive between the mounting button and glass. In fact it's best mounting the button by itself first in order to achieve the best bond. Lightly sanding the button with Emery cloth against a flat hard surface until its clean of all adhesive residue then clean with alcohol or acetone---- wipe that off quickly, don't let it evaporate away.
Using the supplied cleaner/primer apply the adhesive to the button, place on glass then hold for 10 seconds, keep those fingers OUT of the glue!
After 10-15 minutes using a new single-edge razor blade remove any primer or adhesive ooze before re-attaching the mirror and all should be good for another long time.
Hope this helps!