Considering you're in the Bay Area with an unpredictable (if any) first frost date, you probably should let them ride until the foliage starts to die off. This allows more time for the plants to send nutrients to the roots. Then cut the plant a few inches above the ground and cover the crown with well rotted compost/manure... 5 or so big shovel-fulls per plant should do. A mix of bagged manure and compost available at any big box hardware store works fine too. That will provide a good slow feed over the winter months... or should I say "cooler months" for you.
One consideration for this temperate climate is bugs/disease that may take hold in the ground level soil amendments over the wet winter. Perhaps some other local growers can weigh in with their experience.
It's a funny coincidence that I opened a 2013 Old Foghorn seconds before browsing HBT and responding to a Bay Area thread. So delicious!
Considering the length of time your soil amendments may take to decompose might be something to also consider. Compost generally takes much longer to convert to biologically-available nutrients compared to urea, but also contains a wider spectrum of nutrients.
Im in southern California and I let the plants die on the vines at the end of the year. Each line dies back at a different time - usually based on the ripening time of the plant. When the remains of the plant look sufficiently ugly, I cut them back to the ground. Over winter, rainfall and occasional watering should take care of the root stock.
After harvest, I use an out of the box 5-5-5 mixed into the top soil. If the plant has shown any hint of nutrient deficiency, I'll toss a fist full of bloodmeal and rock dust in as well. Past that, I usually wait for vegetative growth to see if anything else is needed in the soil.
Thanks for the info Friarsmith, PapabearJay and Voodoo.
It is hard to tell when first frost happens around here, could be Dec or January maybe earlier. I would say the soil never sees sustained frost/freezing just short periods overnight. Sometime in mid Nov. they do look pretty spent and that is when I cut them to the ground. Trying to remember but I think they may still have some green leaves then too.
I did cover with compost the first winter, but with the winters rains here I got nervous about how wet it was around the crowns. I did lose one plant(brewer gold) that first winter, but it did not grow that well so it might not have been from getting too soggy. Adding compost does seem like a good way to add some nutrients back to the soil over the dormant time.