As is well known, an array set up in a non-sealed space will gradually weaken over time, regardless of whether it relies on the Immortal Origin Force of the array master or on immortal crystals.
For an Immortal Origin Force array deployed outdoors, the Origin Force is gradually consumed as time passes, because people or living creatures inevitably draw near and trigger the array, thereby depleting the Origin Force contained within it.
The same holds true for arrays set up outdoors that rely on immortal crystals.
Chapter 3088