When updating your premium theme, you might have noticed that no alert appears in the WordPress admin panel when a new version is available, as it does with the free themes from wp.org. To update your theme(s) without problem, I suggest that you give the following plugins a try. This is instead of going through the procedure of deleting the theme and re-uploading it, with the risk of losing settings.
There is one more area in which you risk losing your settings when updating – your widgets. There is another useful plugin you can use to export/import widgets if that happens.
I hope these 3 plugins can help you when you update your theme. Happy updating!