I depends , i don't bother bonding the lid back on and just use the socket to hold the heat spreader in place. So in reality and unless you need to rma the cpu there is no need to bond the lid back on.
The main reason i say this is while all the liquid metals are very good conductors how long they last is debatable , i have used liquid pro, ultra and the thermal grizzly stuff and had very mixed results , my 4970k requires re doing every year or so , the liquid metal tends to dry out and turn to a flaky alloy along with obviously degrading thermals, yet on my gpu its been fine and was still liquid the last time i cleaned the block. I made the mistake once of using it between a 5960x and a nickel monoblock, it alloyed with the heatspreader and destroyed the surface completely requiring me to lap the cpu.
If you must just use standard automotive Silicone black (loctite 5910/5940).