I somehow missed the smiley off my last comment....
I expect e-mail's during office hours to be responded to within an hour but im not distraught if they are not. It just tells me I am dealing with someone on the ball who is efficient. There is no excuse these days for not responding quickly as people now have their emails sent to their phones etc so technology enables us to be contactable at any time. If a company took 2 days to respond to my email, I would shop or seek service elsewhere.
With regards to a written letter, ive not given it much thought, I have not written a letter in years.