Cambridge dictionary gives this example
We've just spent $1.9 million on improving our computer network.
I am aware of that usage, in the standard form,
spend sth on doing sth.
This post (https://www.buzzfeed.com/eleanorjones/how-i-fell-back-in-love-with-swimming-and-my-body) starts with
After over a decade spent avoiding pools, swimsuits, and public showers, I've found my way back to the water and all the reasons I loved it as a child.
I guess that means the author spent a lot time (over a decade) on avoiding swimming, is my understanding right? In other words, is "spend on doing" a contraction form of "spend time on doing"?