It is my job to sell these thing...
It won't make the pack take more charge cycle by slow charging, but it will make it last longer for every charge, as fast charging usually stop before the batterie is full....(compare this to fill a glass with a 2 inch pipe vs using a spoon... you don't want ANY mess, do you?)
And it is not true that you can't charge above 1C... I only am using GWS cells, and they clearly state this :
now there is an other brand of li-po cells witch I don't remember the name that state we can charger their's at 2C!!