Nothing to do at all about how many times you have visited. For more than 10 years I have visited 40+ times...I treat each arrival as the first time...either just 30days on arrival, or the appropriate visa for my intended stay organised before travel...simple really.
Well, when you apply, you have the option, single entry, or multiple entry, only the visa fee is more expensive for multiple entries. It is there on the application, ........
Do it yourself, takes YOU the same amount of time as using an agent..The agent asks YOU to provide to the agency, all the information that YOU would submit to immigration, if doing it yourself.