Just wondered if there is any downside to building your site and adding content whilst on the temporary address? Will it cause any problems or make extra work when I eventually switch over to my chosen domain?
a) Use a site migrator like BackupBuddy’s “ImportBuddy” to move the site (it searches your database for the old URL and replaces them with the new one).
b) Use a plugin like this to find and replace the temp URL and update it with the new one: https://wordpress.org/plugins/velvet-blues-update-urls/
Note: You may need to re-upload your header/logo through the Customizer when you move the site – for some reason that URL doesn’t update.