You can pause your account at any time however your membership’s expiry date will not be postponed.
To pause your account hit Settings then
Account Settings, tap 'Delete Account' then 'Pause account'. This will hide your profile from others and will lock your inbox.
You can un-pause at any time by simply logging in with your username and password.
If you don't wish to pause your account, you can also adjust how visible your profile is by going to Settings then
Privacy Settings.