HI everyone- just a quick update. I left both wheels in there for a few days, but it didn't matter; once she saw that new wheel, it was as if the old one never existed, lol!! She took to the big one right away, and I put some bedding on top of the old wheel to see if she'd still use it, and it hasn't been touched since!! She's using the new wheel the same way as the old. I just love how so much personality is crammed into such small precious creatures!!