I don't think it used to do this, but now when I edit a blog (from earlier today) after writing the edit, it gives an error message saying too much time has passed to edit the blog, and the edit is lost. Luckily I had not typed a great deal. But it strikes me if there is a time limit for editing blog posts it should not give you the option to edit, to save the wasted time making the edit.
However on balance I am not sure that having a time limit for editing posts is necessarily a good idea, as there may be good reasons for needing to edit (perhaps a link has changed, or image hosting site has changed, or error needs correcting). Maybe there is good reason for it, or it is simply a bug.