In my last job as a configuration manager, I, with some trepidation, established a numbering scheme which allows 1.9 ⇒ 1.10. In the end, it turned out not to be a problem. The one downside — inconvenient ordering when you do a default "asciibetical" sort — was very minor and almost never a problem, in contrast to the upsides, which are not having to allocate an expected maximum width for the numeric fields, not having to remind your users to pad with zeroes, not having to worry about software interpreting the number as base 8, and so on.