But performance charts indicating that CM Master Gel Regular is little better that Arctic MX4Hey there,
In terms of thermal conductivity, the CM Gel has a rating of 5 W/m-k, and the MX4 is 8.4 W/m-k.
Regarding how often to replace the paste. That's different for every one. If you take your CPU cooler off (or strip a laptop cooler/heatpipes) then you must replace the paste each time you do that. Outside of that, probably every 2-3 years is okay. With a gaming laptop maybe every 1-2 years.