I've had this issue for months now. I have been dealing with iDrive support since Sept 1st. They have offered nothing of substance, and advised that they do NOT limit bandwidth.
After much persistence, I managed to get a full backup of my drives uploaded/archived to iDrive. I recently had to perform a complete drive wipe and was able to restore all files via a local copy I had. Afterwards I setup iDrive to once again begin to backup the drive. Even though everything was already backed up, the process is now taking as long as the first backup did - ie: weeks.
I suggest that people using iDrive consider other backup alternatives. They offer no relevant support and frankly I'm not even sure if they have my original files backed-up, as it appears it is all being backed up again.