The number of messages in your inbox is entirely a matter of personal preference. Having more in there does not affect the performance of your email or other any of your devices. The number of unread messages in any given mailbox is similarly left to the user’s habits.
That said, I myself have undergone a minor maturation recently, in that I finally recognize the value of keeping one’s inbox clear. I learned to change my ways because Gmail makes it so easy:
All you have to do is “Archive” your messages. That takes the messages out of the inbox but leaves them in the “All Mail” folder. (In Gmail-speak, it removes the “inbox” label.) Messages are still there, still searchable, but totally out of your way.
The Apple Mail apps are not great for this procedure, but the Gmail web site does it beautifully. You’ll see the Archive button right up top. I select multiple messages using keyboard shortcuts: first, the up and down arrow keys to move between messages, the “x” key to select, and finally I hit “e” to archive.
To Archive all of your inbox, click the Select checkbox — the master one, the little grey square that sits to the left of the “Refresh” and “More” buttons. That selects all the messages on the page, and you’ll see this text at the top of the message list: “All 50 conversations on this page are selected.”
Next to that, click “Select all xxx conversations in ‘Inbox.’”
Then click the “Archive” button that now appears above the messages, the little box with the arrow pointing down.
BOOM: Inbox Zero!
And now, here’s my newest new way of doing things: I’ve now started using an awesome free iOS app called Mailbox. It is one of a breed of mobile apps helps me process email much faster, by giving me a single button that will archive all my read messages.