I don't have these jeans, but when I have questions like this, I often call a store or two and speak with a SA. Often, the people working in the store wear the items themselves and know what happens as far as stretching out, etc.
You could leave the tags on and wear the jeans around the house all day to see what happens. But if you're like me, you'll probably spill something on them and not be able to return them, ha ha.