A timing belt is not something that needs to be replaced so often. Did you buy your focus new? If so, you better get that looked at soon to make sure it's ok. If you bought it certified pre owned, it's probable that the dealer had that done already some time ago. As long as it's been done once before the 100k mark, you really don't need it again. It's not something that has to be done every 10 k miles or anything.