Dude, Elgin eh? The name just caught my eye; I drove through there a few weeks ago on my way to a KOA campground in Union, IL.
Anyways, to your question: I don't think that my infantilism will ever go away. It can be more or less intense depending on what's going on in my life at the moment, but... the desire is ever-present, even if it's only in my subconscious mind at times. *Shrug* I've never had extreme guilt over it; I've never had binge-purge cycles or intense feelings of loathing; I just kinda deal with it.
The first signs of infantilism in me showed up when I was three. I'd like to say that I've spent the last 19 years completely shame-free over it... At the age of 5, I learned that wearing Pull-Ups (from a pack purchased for my stuffed animals--lo and behold, they fit me) was not socially acceptable; I don't believe my parents had ever (or ever again) yelled at me so much. So I figured something was kinda off about it, but I didn't take it too much to heart. I just figured that this was something my parents didn't need to know about.
My best advice would echo what others have already said: accept your infantilism for what it is because beating yourself up for something that is likely out of your control is... pointless and a sad way to spend one's life. Don't let it overshadow your entire life (diapers are hardly a good substitute for friends, family, relationships). And as for relationships (possibly the most difficult bit of my self-acceptance spiel), well... one's significant other should probably be told about one's infantilism at some point, preferably waay before marriage. Granted, it will make finding an accepting mate more difficult, but I think finding someone who accepts ALL of oneself would be worth the effort.