I guess so. I also wonder if they knew how many hours is behind the extra work i did. I might consider itemising how long some of the extra jobs take in the invoice so they are aware of what they got in the final product. At the end of the day i did the extra stuff to help them out. They may be unaware just how much i did.
I think i'll continue giving a few extra freebies here and there, but make sure people know what they are getting. Although i am generally just being a nice guy, i do expect thanks, in the same way that if you helped someone in the street you would expect an appropriate thanks. Doing approx 1 day additional work for someone deserves more that just a two-word email when the final product is delivered. They are good guys so i will definitely pop in and see them when i'm next in their area to see how they are using the photos.