Absolutely; the Listing Agreement can be set at any interval you want.
If you've had it on the Market for six months, why hasn't it sold?
The "Time on Market" varies a lot around California; probably averaging 90 days.
Willow Glen is a nice area: Without knowing more details, I would guess that the Listing price is too high. That is true in about 98% of the cases. Sorry, but that's the truth.