Sorry for asking underclocking question in a overclocking forum

Im using AMD PhenomII x3 720BE unlocked to x4. I want to leave my pc online when I sleep to seed torrent & downloading so I decide to underclock my 2.8Ghz to 2Ghz or even lower. Currently I'm using AMD Overdrive and I reduce my multiplier from 14x to 10x and it manage to go down to 2GHz. I just wonder if I still or should reduce other stuff such as voltage or etc? Do underclock really reduce heats which prolong cpu life?

Thanks for your reply

I dun mind abt electricity bill..im staying in uni hostel and no matter how much I use, its paid =P

if undervolt, temp will go down?o.o