I have been using an agent for my EOS based on marriage, for me, it is worthwhile because there are so many documents needed, and I don't have to spend a whole day at immigration. Or get there and find out I need another document and have to go again. They get an appointment for me, and I go sign everything with my wife and we are out in about 30 minutes. They even go to the amphur and get the updated cor ror 22 or whatever that paper is. If I ever switch to retirement extension maybe I will do it myself since there is less paperwork.