Yes, deadheading helps. I just cut back all my mint and I prune back my thyme regularly.

And it may be a locational thing but I never really "harvest" any of my herbs for drying or freezing etc., but pick them fresh as needed year round. About the only one that does not produce in winter are my chives.

Dill defeats me too, year after year. 😕

Many herbs are evergreen, so I don’t harvest them for storage. Parsley and mint also usually keep going sufficiently to have something to pick year round, especially if you put a cloche over them. To keep the mint at a good quality cutting it back helps. That way you have a succession of fresh growth. If it is allowed to flower the stems get tough.

Basil I just use in summer when it’s possible to grow it here, albeit in a greenhouse. And I freeze pesto.

I omitted basil from my comments as I am one of those that dislikes the taste of it intensely. Same with cilantro :-) Both are annuals so unlikely to winter over and if I did like them, those would be ones that would be harvested and frozen or dried for future use.

Deadheadibg is clipping flowers ( which will cone back fast). Does cutting back mean to the ground? To the first leaf?

Cutting back is any amount you like. Just cut to a robust looking point. Dead heading individual racemes on mint is time consuming. Quicker to just chop off the tops off the plants. Mostly, for me, it occurs simply by harvesting.