"Yeah. I can only phase through something as long as I can breathe. If I'm phasing through something that doesn't have any air, like through the ground or a wall or other tight space, I can only phase for as long as I can hold my breath."

Which, has gotten to be a good bit of time nowadays. But she still need to breathe eventually.

"Yeah. Some people can hold their breath longer with training, but we still need air."