To the thank you question – I would answer yes. If someone does something nice or generous for you, then you should say thank you over and over. I do not believe you can actually thank too much.
To the bless you question – If you are a person that bestows blessings on a sneezer, then I think one bless you is fine. It becomes a bit embarrassing for both the sneezer and the blesser to go on and on.
What about you? Do you have any questions for Ask Angie?
You can write me QuestionforAngie(at)