Double spacing after a period has never been proper. There are a lot of theories about why it started, mostly associated with spacing for type-setting or manual typewriters. But if you look at any professionally set document, newspaper, magazine, book, etc., you'll see that a single space follows all punctuation (it's hard to tell sometimes with full justification). If you look at any of the professional style manuals (Chicago Manual of Style, The Associated Press Stylebook, Elements of Style, MLA Handbook, etc.) they all say that it is okay to use 2 spaces, but the proper spacing is a single space after all punctuation.
I'm 51 and I hate when a document has two spaces after a period. It makes for clunky reading and looks horrible.