Had mine re-gassed at the weekend. The first time I've ever had it done in the three years I've owned the car, and I have no record of the previous owner having done it. My car is a 2006 with about 99k miles.
My aircon was still working, but the air was only slightly cooler than ambient. I used the Kwik-Fit service (£59.99) and now it's much much cooler. It took them about 30 minutes. I noticed afterwards the L and H caps were loose, I assumed they weren't supposed to be and screwed them back down.