I don't usually worry about it either but it starts saying days and continually gets longer, it gets my attention.
I ran a defrag again, and all of the disk doctor type programs. Overnight it finally did the first scan and started actually wiping. The projected time has been at about 6 hours since I checked this morning, (5 hours ago). At least it isn't piling more time on top. It was at 1% this morning, 17% now. That's where it got hung up last time so I hope it keeps going and actually gets done.
I must have needed a few days off work since I can't do anything until it's done.