I believe people are seriously misinterpreting Liandrin’s statement.

I don’t believe it has anything to do with strength in the One Power nor skill in creating the weave. It’s purely about being tired out from having to maintain the shield constantly.

Imagine you’re holding someone prisoner in a room where the door has no lock. So all you’re doing is leaning into the door, to hold it closed. The person trying to get out can afford to take breaks, resting between attempts. But the person holding the door closed has to remain in position, and can’t let their guard down for a moment.

It’s got to be exhausting standing guard while Logain can sleep, pretend to sleep, relax, push on the shield periodically to keep the jailers on their toes, etc.

You can tell this by looking at Logain and all the women in the cave when Liandrin says this.