When you're using Inbox Zero or trying to get there using Gmail's Priority Inbox, you'll need to tweak the way that you check your inbox in order for it to work well. All in all, you're just ensuring that you don't obsess about your email too much.
Depending on how well you've optimized your morning routine, you might have time to check your email when you get up. It can take anywhere from 10 minutes to an hour, depending on how much email you usually receive. The trick is to stop multi-tasking for this and concentrate on getting it done. Sometimes I manage to complete it in 15 minutes while other times it takes up to an hour, especially when you are replying to work-related emails.
It's usually best to check your email a set number of times every day. I've found that 3-5 times works well in my case, but if you receive 50-100 emails every day, then you'll have to check it more frequently. Once I'm in my inbox, I go through the emails and notifications quickly with a glance. I address those that take a few moments to answer: family, friends, Facebook notifications, etc. These are examples of emails that either can be addressed quickly. Alternatively, if you receive important family news, you'll want to reply appropriately. However, this happens rarely in my case. Once I've dealt with 10-50% of the emails this way, I'm left with a core number of emails that need to be answered and usually require some research, checking of facts/figures, and thought.
The emails are usually replied pretty quickly. Once that's done, I can concentrate on sending emails that I need to. Some might be queries, quick replies that I've gotten from people around me, or more comprehensive emails, which take longer. When this is completed, you can log off, which is what I do. Even when I'm home, I never leave an open email tab in my browser. I tend to do a lot of work in the evenings. When I'm done, I check my email one last time before closing my Google Reader and Twitter, effectively spending time off social networking completely and relaxing.