I've had several players contact me during the last couple of months saying they're going away in less than 48 hours (sometimes like two hours!) and could I possibly find them a temporary replacement.
I don't know where this has come from, but please take note:-
1. It is not the GM's job to find substitutes (please don't call them replacements - here at least that means permanent). If you are going to need a sub then start looking early. You'll usually find somebody if you give yourself time.
2. If you have a holiday, a stay in bospital, or anything else that will take you out of games for a time, planned then let the GM know as early as possible so that she can plan ahead as well. I don't know about all the other GMs,but my HouseRules are clear - if you ask for a delay at the last minute you won't get it unless there's a real emergency which you couldn't plan for. Delays are bad for games - more games fall apart because of repeated or long delays than any other reason (except, recently, GMs walking out, which we're doing something about on our side!)
You're the person who knows what you're planning, it's up to you to deal with it!