Not too often if you keep the writes to the SD card down to a minimum. I would say at least 6 months with normal logging/updates/cleanup/wear and tear. But if you are concerned check out a WD PiDrive. Anywhere from $15 to $30 you get 64GB to 375GB on actual hardware which wont wear out in a few months.
My PiDrive has been rock solid since they initially offered the original 314GB drive for $31.41 on a Pi Day awhile back but well over a couple years. Oh the irony of the price and size!
Install Raspbian/PiAware image.
Copy everything over but /boot to the actual hard drive.
Make a couple changes to system files.
Decide to go that route let me know I have a post on how to do it elsewhere or actually on this forum come to think of it.
Just learned PiAware is tied to the software now and not the hardware. I don’t think I like that being before adding an actual Western Digital hardrive to my setup I was tossing SD cards in the trash much more often than Raspberry Pi’s…