Another elementary question, I'm afraid.

What is the latest thought on this issue?

Specifically:

DTW-SFO-DTW, no Sat nite, in January, prices out around $1000.

DTW-MEM-ATL-MSP-SFO-DTW-EWR prices at $401. What risk if I just exit the plane in DTW on the return, and not take the last segment?
I could if necessary buy a one-way EWR-DTW from DL for $194, but want to avoid the time and the expense.