keep in mind that those IO are human just as we are.
it's like... even if they were given no policies or training in how they should handle others age difference, they will become suspicious if the age different is huge no matter what.
this is why it's so important how you (and your spouse) present yourself.
i just got approved for my GC and my wife was 19 and i was 20 at the moment (yes the marriage was completely real!! our entire family attended the wedding in her hometown @ texas!)
anyways, when we were walking out of the interview room and through the isle where everyone else was waiting, it felt like they were all staring at us as if "they weren't in their as a married couple interview, were they??"
this is what we worried about the most before going to the interview (how IO viewed us, don't care about other people) and i'm sure he noticed and gave us an extra hard time. after all though, it turned out fine because we had all the evidences and proved that our marriage was real.
for you, kanani, i don't see much that you shold worry about personally. make sure you have all the sufficient evidence and i think the fact that you two have been married for so long looks very favorable toward you.