Iguanas will, unfortunately, sit in cold areas until they freeze or dehydrate. We've seen (over the decades) many reports of iguanas choosing to spend the night on windowsills and being found dead from freezing during the night. Once they get very cold they can't save themselves.
Ceramic heat emitters are long-lived, which makes the initial price well worth it. Most of mine survived more than 5 years, and a couple of them made it past ten years. Just never bump or knock them, and keep spray-mist away.