If you want to be really hard on your 75GXP, put it in a sandwitch between two other hard drives (preferably two old 10Krpm SCSI drives like the first generation Cheetah) with no active cooling, then pass a few hours to reboot the system every 30 seconds or so. If the drive still doesn't fail, make it run IOMeter vitam eternam for a month or two and then shut down the system for a few days. When you'll reboot, there are good chances your drive will be R.I.P.
Drive running 24/7 are more prone to fail when rebooting than drives that boot every day due to the accumulation of junk on the bearings. When you power down for a few days a drive that use to run 24/7 for a while, the "junk" sometimes solidifies and break the motor at the next power up. It isn't such a deal for SCSI drives with high quality components, but a 75GXP with parts that might fail just by looking at them is another story.
However, I heard that the main reason behind the high failure rate of the 75GXP is related to poor heat resistance, hence my suggestion of putting the drive in sandwitch between two others with no active cooling.
Good luck, if I can say it that way.