Growing Herbs.

Is it better to grow from seed or buy new plants every year ?

Most of the perennial herbs are quite easy to propagate from cuttings when they get too straggly and/or woody - this would include sage, thyme, and rosemary.

The annuals/biennials that Sparkyrog has mentioned can be grown from seed or you can buy plants if you prefer (I've done quite well transplanting the pot-grown parsley sold in supermarkets - plenty of plants there!)

French tarragon is almost always propagated by division of existing plants, although it is a perennial given good growing conditions and not too severe winters.

Most of the herbs I grow are perennials like French (not Russian) tarragon, mint, sage, marjoram, thyme and rosemary. I grow parsley from seed but you can grow coriander as well.

I buy mine, especially lavender and rosemary. Cilantro hasn't popped it's head through the soil yet but I'm afraid when it finally does it'll be too hot and it will bolt. Basil is easy to grow from seed, and while I've down some this year (and parsley too) I'll probably end up buying plants. I think it depends on whether or not you have the space to start them and how easy the herb is to grow from seed. My lavender made it through the winter, although it looks a bit scraggily, I might try to root some cuttings of it. Mint and lemon balm died back during the winter but are now growing in full swing.

Put in a Borage root last year it came up it died ,it came up it died ! this year completely unexpectedly it has come up and is growing like a weed 

I've got a parsley plant in a huge pot on the plot - it will be the third year that I've been able to harvest from it. It gets woody at the end of the summer - I cut it right back to maybe an inch high thinking 'that's that then' and so far its come back each spring. Can't get one to do the same at home... 

Wow three years, I only get a two year cycle of my parsley, it just twindles away after that. I cut mine down like that too.
Started a new load off early this spring for the next two year period. I grow mine in 11" pots, sow and start the plants off in the greenhouse.