If you are happy with your aluminum bike go with that.
I am a big believer in going with the bike you have (kind of like donald rumsfeld)
rather than the bike you would like to have.
However I have just been reading Stephen Lord's
Adventure cycle -touring handbook and he says this about frame materials:
Chromoly steel is therefore the obvious choice for bike tourers who want to wander far. Should you need one, steel weldeers exist in any small town; aluminum welding is rare and specialized. Whatever the virtues of aluminum -either its looks, or the few ounces saved - it's an unnecessary and entirely avoidable risk.
Contrary to what seeker asserts, if you read the tales of people doing expedition touring in remote places, you come across times when local welders patched together a broken frame on the spot. It does happen.
I have seen steel frames break, usually from a crack that propagates, but I have seen aluminum frames break before my eyes, quickly. One of them was a new touring bike from devinci. They replaced the frame under warranty but my friend had to replace all the parts himself.
If you were thinking of getting a new bike anyway I would get steel. If you are short of funds and you like your aluminum bike, use that. On the big scale of things, breaking a frame is relatively low on the list of things that can go wrong.
The important thing is to just go.