It has been noted by UBI that if you do not change your hardware "too much" (and a new GPU for example will not count) then you are ok as it will not use an activation. However when I asked in their forum what actually will make the game activate as such I was told not too worry as I would get further activations upon request.
I was not worried, per se, I just wanted an answer that I never got.
When 1404 first came out they were having issues with the activation servers and I could not get mine to activate, legit bought copy. I kept trying over a few days to then find, even though it never activated, I had used up all my activations..!!
I contacted UBI and raised a support mail but got no where. Phoning them at the time was a no no due to it being premium rate. I never got to play that game again until they patched it to remove the DRM.
So with the vagueness about what counts or not I have decided to not bother reinstalling it until I make my mind up about a Z77 rig, as that will count for sure.
With this type of DRM in future I would think twice before buying the type of key that I did.