Keeping up with email is one of modern life's most universal tasks. If you would like to try a different visual approach to staying up to date with your Gmail inbox, then allow me to point you in the direction of Reply Now, an extension for Chrome or for Firefox.
Reply Now is blissfully simply in operation. Install the app and then refresh your Gmail tab; a browser restart is not required. After a second or two, you'll see the timestamps along the right edge of your inbox for emails received within the last week replaced with color-coded timestamps showing relative time. That is, they show how long ago each message was received. For emails that arrived within the last 15 minutes, the timestamp is green. After 15 minutes, the timestamp turns orange. After an hour (and up to seven days), the timestamp turns red. Anything older than a week features the regular Gmail timestamp.
The Reply Now extension does not let you change any settings such as the time limits or colors of your timestamps, but in a comment on Lifehacker the developer says these two requested features will be included in the next update. That way, you will be able to stretch out the times for a personal Gmail account, for example, that does not receive mission-critical emails requiring immediate responses and where taking a day or two for a thoughtful reply is more than acceptable.