Why should I upgrade?
Your website, your domain
It's your website after all, and at some stage you would want to view it at your own domain, and more importantly, you would want your visitors to view it at your own domain too.
Your content, your domain
You are creating unique, relevant content on your Tank site, but, if you haven't upgraded, this content isn’t attributed to your own domain - it’s attributed to a (development) subdomain instead. Other sites might start linking to you and they would link to 'yoursite.withtank.com' instead of' yoursite.com'. Search engines will earmark the subdomain too. These are small differences but it will make a huge difference in the long run.
Your brand, your domain
Besides these reasons it is nowadays expected that any venture has both their own site and email on their own domain. It lends both authenticity and credibility to any business or individual.