I do not recommend you to connect and disconnect too much times - almost all database servers think that this is a spam and drop connection to mysql server. You will get loooooong time lag and error exception in Unity. So, keep in mind not to fire this two actions very often. As for me this action can be called once or never in your project. Your database will close all "Sleeping" connections by itself. But if you want to use it - think where to use it.