I didn't mean every last vendor, but for the main ones, they really appreciate it. They keep letters thanking them and telling them they did a great job in albums, on a bulletin board on the wall, on their web sites (they ask permission for that); it's good for business, so they really appreciate them. Builds a good relationship for next time.
Sometimes if they did an exceptional job, or I know them personally, I make a donation in their honor to a charity they like or give them a small gift. I once baked some goodies for the desk staff at a hotel that was outstanding for our guests.
You did a great job on your thank you notes, menley! I agree; perfectly acceptable time frame. As you probably know, you didn't have to wait to open the gifts until after the wedding, but with such a short delay, it's inconsequential. Some couples do the opposite of what you did: they write to each other's side. Makes a great impression, and it's even a little flattering to the guests: "Hey, Durwood, did you see that this thank you note from Petunia and Cuthbert was written by Cuthbert? Wow, she married a jewel; I hope we get a son-in-law like that, too. I didn't even think he'd remember who we were, and he wrote about what good dancers we are." (Of course, Cuthbert did not, in fact, remember them at all and was given the info necessary for a personal note by Petunia. No matter!)