The rebuild is usually quite quick, however I repaired a friends TiBook and it took about 4 hours because of all the problems found with overlapping files etc. Diskwarrior did display a message to the effect that there were major problems encountered and I wasn't sure if it had hung or not at first. It did finish eventually, having recovered a load of files and fixed a litany of problems. Bottom line, if your drive has a lot problems it really can take that long. If it takes that long the second time round though, or doesn't complete after being left overnight, then I would start worrying about the possibility the drive may be failing. In that instance, my next step would be to backup the entire drive and then do a low-level format to re-map any bad sectors before re-installing and restoring. Not my favourite way to spend a day but sometimes necessary.