ESP artifacts still have a shelf life, but they will never lose their ability to receive ESP transmissions - only transmit. So if your ESP artifact runs out, you'll still be able to "hear" ESP per usual, but you won't be able to transmit your own messages until you get a new ESP artifact.
There are future plans to further develop this concept, like having transmissions have a chance to be occasionally fuzzy, faint, or indiscernible at low duration.
ESP artifact duration tweak
ESP artifact duration tweak
<Rias> PUT ON PANTS
<Fellborn> NO
<Fellborn> NO