It's not adviseable to do that since you want to have a uniform covering of thermal paste between the cpu and heatsink. If there are gaps and the heat is not dissapated properly then the cpu can overheat and shut down.
I did this once with my phenom, it didn't cause any problems (ran it for a year before remembering about it! )
but this was out of pure desperation, not having any paste, and replacing a dead motherboard!
but i admit its a bit stupid to do this, i did notice more stability when using it for lengthy times after replacing the paste.