Yep, I had mine replaced 3 times! Seems the 3rd time was a charm as it hasn't come un-glued yet (of course, it hasn't been real hot either). What they told me they did to resolve the issue may not make you happy though.
The first two times before taking the old emblem completly off, they marked the tank with tape for the correct (factory) location. The 3rd time, they actually moved them emblem a millimeter or so (I think forward) to fit the curve of the tank better. Their theory/explanation is that Harley was off a little when applying it at the factory.
Seems to work, and I haven't noticed an eye-ball difference in symmetry from side to side...but, I haven't got a tape out and measured it either (because it will bug the sh!t out of me).
Good luck

If the emblem doesn't match the curve of the surface of the tank, it will always be under stress. Eventually the bond will fail, the only question becomes which bond is weaker, the one of the tape to the nameplate, or the one of the tape to the tank.
After marking the "stock" location for reference the installer should lay the new part up against the tank before pulling the backing of the adhesive and move it around slightly until finding the location that allows the nameplate or molding to lay against the tank with no gaps (don't apply pressure to the plate). Mark that location. If you can't find such a location, either get a new nameplate or gently bend the one you have until it will lay up against the tank with no gaps.
The problem could be the factory didn't locate the nameplates correctly in the plant, or it could be the nameplates weren't made with the correct contour to match the tank, or even the contour of the tank could vary. Getting them to stay in place may require a little more work than just taking them out of the box and slapping them on the tank. Once you get them to lay up against the tank with no gap, then it's just a case of prepping the surface properly and applying the nameplate with even pressure along the entire length of the plate. Warming both the tank surface and the nameplate will also help to obtain a better bond.
Jerry