Epson FastFoto 680W is what most people use for scanning their collections which scans the fronts and backs at the same time.

(For flatbed scanning, I actually made a Mac app to help scan fronts with backs, lol. https://timelinescan.com/frontback-scanner [it's not as refined yet])

Getting handwriting from the back along with a potential date make scanning the backs worth it, for me, on a flatbed.