I think the only time you should ever repaste is if you have removed the heatsink. Also, if you are having thermal problems, then repasting might be in good order to troubleshoot what is causing problems with heat.
New thermal paste doesnt transfer heat as well as matured thermal paste. As the thermal paste is heated everytime the CPU is turned on, it finds its way into grooves and spaces in the HS and CPU. This is why your CPU temp is much warmer when you put on a new layer of paste compared to several power cycles later.
Intel E6750...........PSN: ELBATROP
XFX nForce 650i Ultra
Patriot PC2-6400 8GB (4x2GB)
36GB WD Raptor
Samsung SyncMaster 931c
Samsung SyncMaster 750s
Windows 7 Home Premium 64