When to sanitize pumps ?

I breastfeed my baby, and pump sometimes only to build a stash for special occasions when I'd like to give her a bottle. I'm confused as to when I should sanitize though, I wash the parts when I'm done with it- but should I sanitize the parts after washing, or before I wanna use it next ? I thought I read somewhere that sanitizing your breast pump parts, it's only actually sanitized for so long. And when you sanitize, obviously you have to let the parts dry as well. What are your breastpump cleaning routines ??