My first publisher and I used to go around and around about this. I preferred to use “till” in many cases in place of “until.” She insisted that when I do that I must use “’til,” reasoning that it was the abbreviated version of “until.”
This, however, is based upon the false assumption that “till” is a derivative of “until.” Not so, Grasshopper–and, in fact, it’s quite the opposite: “until” is a derivative of “till.” “Till” existed in the written language as far back as 800 A.D., and it meant just what it does now: “until.” On the other hand, “until” didn’t appear in the records for another 400 years, around 1200 A.D. Originally it didn’t even mean what “until” does today. That meaning survives in the archaic word “unto.” However, by about 1300 A.D. both “till” and “until” occurred side-by-side in writing, both having the same meaning as they do today.
Now, in my publisher’s defense, “’til” is not technically incorrect, usage-wise (although it is incorrect etymologically). It can be used as an abbreviation of “until.” It’s just that there’s no reason to do so. “Till” is a perfectly fine word, and, IMHO, it looks better on paper than “’til.”