Do you back up your cell phone?

Have you ever backed up you cell phone? I did but it was long time ago. Maybe about a year. Now, I have a new phone and I just transfer my data from my old phone to the new one without using a computer. It only needs a bluetooth connection and done in just under a minute. It is so easy, I didn't expect it. But, I never backed up the data after I was done with the transfer. So, do you ever back up your cell phone? How frequent do you do it?