How big is TOO big?

So my beautiful leopard gecko Marble's is growing more and more each day. Not sure on the gender yet, as Marble's is only going to be 4 months old on April 14th, but we're assuming female until we see hemipenal bumps. She's 52 grams and 10 inches long and still growing. We got her from a basic pet store so she definitely does not have giant genes in her.

Anyways, we want to upgrade her tank from a 20 gallon high tank to a 29 or 40 gallon. Is there any reason why we shouldn't? She utilizes all of her hides, but they need size upgrades because she can't fit and she can barely move around comfortably.

I heard to main concern is heat, but we would obviously give her an appropriately sized heat mat so she doesn't loose her warm side. Would there be anything else we need to worry about?

I'm sorry for accidentally posting this twice in a row but I can't figure out how to delete one. I did not mean to spam.

Don't worry, I"ll delete it! For a gecko that size, a larger environment sounds great and I would imagine she could handle either of your proposed sizes.

Aliza