I use both until and 'till but thought I would have a look on the web and found the following usage guideline in the
Oxford Advanced Learner's Dictionary
till /t{I}l/ conj., prep., noun, verb
> conj., prep. = until: We’re open till 6 o’clock. * Can’t you wait till we get home? * Just wait till you see it. It’s great. help Till is generally felt to be more informal than until and is used much less often in writing. At the beginning of a sentence, until is usually used.
<snip>
©Oxford University Press, 2005.