I bought a Noctua NT-H1 thermal paste last January 2012 and I haven't yet used it, though I already squeezed a tiny bit in order to check out the paste. My original plan was to reseat my CPU cooler and use the NT-H1 and hope that my CPU temps would go down by about 2-3 degrees Celsius. But I thought that the effort of having to take apart my computer might not be worth it because I may end up not gaining anything. I might just use it on my next build or when I find time to reseat my CPU cooler. Can it last for another year?
More aboutlong thermal paste last
Many, many, many years.
A lot of paste lasts up to 10+ years.
Since zinc and aluminum paste with silicone base and graphite pastes are practically chemically inert, a quality thermal paste using any of those has nearly unlimited shelf and service life.
The shelf life is largely limited by the amount of time it takes the colloidal paste to settle which would let the powder clump/cake up and render the paste unworkable.