Can the Mirror of Life Trapping force multiple saves?


The Mirror of Life Trapping can trap creatures in it.

Any creature other than you that sees its reflection in the activated mirror while within 30 feet of it must succeed on a DC 15 Charisma saving throw or be trapped, along with anything it is wearing or carrying, in one of the mirror’s twelve extradimensional cells.

Does it force multiple saves? If someone stares at the mirror a remains there looking at themselves for 5 minutes, do they have to save more than once? Or only every time they blink?

What if they look away and look back on the mirror?