Zhège xiàngmù qiánqiánhòuhòu huā le sān nián shíjiān.
This project took three years all told.
Tips
usage
Reduplication of 前后 (before-and-after) into AABB form turns it into 'the whole sequence' or 'every aspect'. Often introduces a full retelling: 这件事的前前后后… ('the whole story of…'). Can also describe physical thoroughness — checking front and back of something.
grammar
Functions as a noun ('the whole of it') after 的, or adverbially ('thoroughly, all told') before a verb. Compare with 来来去去 láiláiqùqù ('back and forth') — same AABB pattern, different paired verbs.