I am afraid so. You can only manually sync once every 24 hours if you are free user. :(

If you want to enjoy auto sync and limitless manual sync, you may consider upgrading a Pro account. We now also support paying by Google Play.

In addition, after becoming a Pro user, you can use some cool features that are exclusively made for Pro users, like Goal, Subtask, Add Task via Email, windows/mac version ...

http://enblog.doit.im/post/25994485658/how-to-add-task-via-email
http://enblog.doit.im/post/42475480144/introduce-goals-and-subtasks-to-doit-im-for-android

Thank you for your feedback and support.