Age is a big deal for non prior military applicants. The likelihood of DOR goes up dramatically after about age 25. They have decades of data on this. One of the reasons they give waivers for prior service is because a vet is less likely to DOR. They know what they are getting into. They have already experienced the shock indoc to military life once before. A vet already has years invested in the military toward retirement. A 29 year old prior service guy is less likely to DOR then a 24 year old off the street.
The information that was given to us by the OPS officer at OCS several times while I was there was that prior enlisted were
far more likely to DOR. The OPS O also said that this was part of the reason that they make them show up with uniforms ready to wear in the event that they do DOR. My own experience would back this up. I saw prior enlisted (including one roomate that lost his mind the night before RLP) DOR 3 to 1 over civilians. The resounding theme was that they would rather go back to their old job and finish out 1,2,3... years than deal with all the bullshit that is OCS. Take it for what you will, but that was my experience.
As for the OP, get on top of things and get to OCS. You are a big part in how fast your application goes through. If your recruiter gives you something to complete, get it back to him the next day. Chances are he will see that and put the same amount of effort in to your package. It worked for me.
My only other advice would be to take an honest look at yourself and ask yourself if you will be able to handle OCS at this part of your life. I saw some of the older guys (and women) have a hard time dealing with issues that their younger shipmates did not necessarilly have to deal with. At 25-30 years old you probably have established yourself in life more than a kid fresh out of college. Things like a mortgage, and other payments, a wife that may not understand what you're going through, kids, or God forbid a divorce, are all things I saw some of the older guys struggle with while they were there. Try to take care of these things before you leave as best you can. Make sure that your family or your personal finances function autonomously without you for 3 months. Try to mentally prepare yourself as much as possible so that these things aren't laying a heavy burden on you mentally. Take my advice for what you will, but it could make things alot better for you and decrease your odds of DOR'ing. I know your questions were focused on the application process, but hopefully that can be of some help to you when you do get in to OCS. Trust me you won't be the oldest guy there.