As a DM, I disagree. A day or so is an emergency cancellation (if you're the DM). A week or two is fine if you cancel rarely. If you keep scheduling games, though, then cancelling them, even with a week or more's notice, that's rubbish. You're basically pretending to DM, and giving people false hope.
If the OP is going to be out for, say, three months, as he was before, then he needs to tell the players that, sooner rather than later. They may well want to set up their own game instead.
If the hobby is something that isn't time-critical, I honestly have no idea why you'd cancel D&D and not that. Like, don't book it if you don't want to run it!