Multiple sunders gcharms active at same time??

I noticed i can carry different suffering grandcharms of the same type (cold in my case) on my sorseress. The negative coldbonus i can see in my resistancestats, but is an inventory full of skillers and for example three instances of sundering more usefull? My sors can have two sunderings (-140) at this moment and still have full resist. If i work around it, incould have three active in inventory and still have full resist.

Having multiple Sunders of the same type yield no bonus effect. A specific type immunity can only be broken once. When immunity is removed enemies are left with 95% of that res. It's redundant tanking your own particular res for no purpose.

However, if you are multi build and you really want to break that many immunities (and you don't have yet or you don't want to use any other source for that, for example Infinity on Merc) you can carry multi different Sunders (for example Fire and Cold on Fire/Cold [Bowazon] maiden). But again, you are giving up on multiple res for a bit more dmg which often doesn't even matter -- multi builds are made for versatility anyway (so you can rely on multiple sources of different types of dmg) but they also offer a way of dealing with "being stuck against immune monsters" when you don't have BiS gear.