I'm curious, I'm in the UK, and I'm assuming the OP is in the US (please correct me if I am wrong!), but my experience of viewing and buying and selling property is that it is not the usual expectation that the householders vacate for a viewing. In fact, in every case I've been shown around a prospective property by the owner, and they have answered questions for me, and I did the same when I was selling. I know the system is different in the US, but is it usual that hosues must be completely clear of occupants or any evidence that the house is lived in by anyone prior to a viewing? Obviously it's better if the place is clean and tidy, but i would be shocked if the occupants of a house I was viewing felt they needed to leave whilst I was there!
To the OP though, an hour's notice before a viewing is totally reasonable in my view, though I don't think there's anything wrong with the realtor making the call to you just to see if a short notice viewing is possible. To turn it around, would you be put out if you found out that a realtor hadn't called you with a potential short notice viewing on the assumption that it could not be accommodated without checking with you first?