I live in California zone 10a with mild winters. I have couple of tomato plants of determinate variety that produced good crop till September/ October after which slowed down but I continued feeding and they continued to produce and still have fruit and flower though less quantity
My question is to know if I should continue feeding or stop now as temperatures now are in 40s and 60s.
Please advise.

I would guess the plant slows it's growth partly due to temps and partly to reduced hours and intensity of daylight.
I would also reduce feeding.
My best guess. Too cold here to have the same experience.

Your tomatoes are determinate? So they should bear a single crop, in a spurt, then die back. Yes?

And have they done that yet? If not, are the fruits still developing? If so, will they make it to maturity before it gets any colder?

Late in the season tomatoes tolerate stress. It stimulates fruit to mature/ripen. So gardeners often reduce water in the late summer. I'd bet the same holds for feeding.

If they are determinate and nearly finished, then quit the feeding.

The important question here is: are the plants in the ground or in pots?
As long as your plants are flowering and bearing fruit they require nutrients. If they are in pots, then definitely continue feeding them, although less than in midsummer if the plants aren't producing as robustly as they were. Same thing applies to in-ground plants, but your fertilizer regimen depends on the soil's needs, which probably aren't as critical as in pots.

Unless you've got a variety bred for cold weather, you'll find that they will stop producing fruit at the temperatures you mentioned anyway. Fertilizer won't change that; they're done.

In regards to determinate tomatoes, do they make the first "main" crop and if left to grow (during normal growing seasons) do they did dribble out tomatoes over a longer period of time? The big indeterminates seem to overwhelm with production. I'm thinking that a flush of tomatoes at the beginning of the season would be good for canning/freezing and then a slower flow of them would be good for fresh eating the rest of the summer. I think @Weedwhacker mentioned something to me some time back that they don't completely stop producing after the main crop. Thoughts?

Ed, that's correct. Determinates usually bear a lot at the same time (not necessarily early; could be mid season) but the ones I've grown continue at a lesser volume until the end of the season. This statement about determinates from above is erroneous:
"So they should bear a single crop, in a spurt, then die back."

-- what Zoë said.

Thanks Zoe and Sandy. That is what I was thinking. I'll go ahead with plans for a few determinates so to have some short plants to put insect netting over. Hoping to thwart those stink bugs this year from ruining the tomatoes!!!