A relative finds the marriage of your grandfather's sister and sends you the

[hurworth]

I sent the information with images of the records a week ago.

[Blackwidowspider]

I had similar. Find a marriage that was only a family rumour... Added it, got the info, emailed the other got a response! And photos! And further info!

[carol8353]

I sent the information with images of the records a week ago.

Maybe the relative is on hols! 

[Sloe Gin]

I'd give them a bit longer.  I'm very good at responding quickly to simple emails, but if I've got a bit more to say I tend to leave them until I have time or am in the mood for a fuller answer.  Unfortunately this can mean they get sidelined for a bit!

[Josephine]

The thing is, if I'm reading this correctly, s/he had time to add the data to his/her online tree, but no time for a simple thank you.

I've had this type of thing happen to me, too. It's not a good feeling.

[Sloe Gin]

The thing is, if I'm reading this correctly, s/he had time to add the data to his/her online tree, but no time for a simple thank you.

Yes, but adding the data to the tree requires no thought.  Whereas composing a reply which may include other info takes up more time and thought.

You are probably right in expecting no reply, but I'm just saying it's the sort of thing I might do.  Add the names in quickly, and defer composing a reply until later.  Then sometimes other things intervene.