Propagating Thyme

We use a lot of Thyme in our cooking, so I try to make sure we have plenty of it in the garden. This has proved harder than I expected. I find that it is very susceptible to insect damage - I think from thrips. Whatever it is, they eat away the surface of the leaves, stripping them of the glossy dark green part that contains all the essential oils, and leaving them brown, dry and unappetising.

I am reluctant to spray edible plants like herbs with too many chemicals, so I have been forced to accept that in my garden Thyme needs to be grown as an annual, not a perennial. Most years I buy a few potted Thyme plants and put them either in bigger pots or in the border. This is one of last year's plants:

They get cropped until they succumb as described above, then are replaced by new ones. This can be expensive, but fortunately this year it probably won't be necessary - because of these:

Last Autumn I realised that my most recent batch of purchased Thyme plants had self-seeded after flowering, so I potted-up some of the seedlings and kept them over the Winter in my coldframe. They are now quite decent little plants.

I have planted some of them in the border over by my fruit trees.

I wonder how long they will survive???