People's expectation clock starts running from the time they hit send. More improtantly, deadlines related to the email content really sets the agenda for how often to check your email.
Then change people's expectations, including those of the deadlines appropriate for tasks communicated by emails that people may not see for a while! (Partly a tongue in cheek answer - I know this may no be feasible, and you make a fair point).
Hehe. Someone called J* wants me to keep her posted when I start my internship. Her perception of my reliability may be consequential to my career in the future! So, I have reason to maintain that perception of punctuality. I have been invited to attend a fairly boring meeting tomorrow with somewhat important people attending, so it might make my life easier if I go and seek some economic rents. Then again I guess it's better to be hated, then love love loved for what you're not.
How frequently do you think you *should* check email? You can also say how frequently you do in comments.
Personally I'm sold on thinking you should check it around once a day, not necessarily without fail. That increases focus on both email and non-email, and minimises getting sucked into distractions. But some people I know disagree. Some believe in getting notifications whenever a new email comes in.
For anyone who'd like to check email less often and uses GMail, I recommend using http://inboxpause.com/ and this full screen compose link: https://mail.google.com/mail/u/0/?ui=2&view=cm&fs=1&tf=1&shva=1
Edited to add: I'd recommend everyone at least try checking only once a day, at least for a few days, to see if you find it more productive and/or relaxing. That'd be a big enough win to make experimenting worthwhile.