Is it common to wear one set of aligners for 1 month?

I reached the last of my retainers and the doctor had me come in days after I should have already switched to new liners. (She was on vacation the week before). We finally did another scan for my next set of liners which I’m told take another 2-3 weeks to be delivered. I’m now in the same retainers for a month and counting, just waiting for a text that my trays are delivered.

Is this common or am I being taken advantage of?