Don't mix print PEA and PES plastics in one channel letter, otherwise the two layers will easily break down.
PES and PES-FR are both PETG based plastic alloy.
You can mix print PES and PES-FR filaments, they will bond together firmly.
So please make sure you are handling the PES-FR filament correctly.
Keep the PES-FR filaments in sealed containers all the time, no matter if it's in use or not.
Under outdoor environment liquid acrylic face will corrode the 3D printed channel in 3 months, so the lifespan of the channel letter won't be more than 3 months.