You are looking for a low average seek time and a low average write time.
You want the hard drive to be 7200 RPM or faster.
You want the hard drive size to be anywhere from 80gb to 320gb, any larger than that will cause the hard drive to be a bit slower.
You want a 16mb or higher Cache if possible.
As for the life expectancy of the hard drive that's hard to determine. I would go with a Seagate Barracuda or Western Digital Raptor. Stay away from: HP, Hitachi, Samsung, Excelstor, and ioSafe.
I myself would go for a 7200rpm Seagate Barracuda.Seagate Barracuda ES.2 ST3250310NS 250GB 7200 RPM 32MB Cache SATA 3.0Gb/s Hard Drive - OEM