*smiles*
They're a 'guest house' not a hotel; so they only have a limited number of rooms ( I think about 15). Those rooms are made up of a variety of types to suit a variety of needs: so they have 2 shared (no bathroom) standard single rooms, X amount of standard doubles, x amount of enhanced doubles, x amount of family rooms, x amount of en suite rooms etc.
If they book out both their single rooms, a year in advance, for 2 nights; they could end up losing out on a single room booking for a week. That person would go elsewhere. Given that there's no guarantee that we will actually show up, they could end up having done themselves out of a week long booking, and all they gain is the 10% cancellation fee.
Smaller bookings (like ours) are easy come easy go and tend to happen nearer the time (unless you're complete fangurls looking to see barrowman!) a week's holiday tends to be booked more in advance.
Seems reasonable to me