Worries over the serviceable lifespan of battery packs have been at the forefront of many critics dislike of hybrid cars. With doom-and-gloom scenarios of pricey replacements and short service life, the pundits have posited the Prius' long-term impracticality. But an Australian taxi outfit has compiled enough real-world data to put that idea to sleep.

With 32 Prius taxis operating in his Cairns, Queensland fleet of Black and White Taxis, owner Graham Boundy knows the truth about high-mileage hybrids - and it's surprisingly good. Each car racks up about 200,000km (125,000mi) each year. Two of the older examples have managed a lifespan of 350,000km (218,000mi) and 550,000km (341,000mi) before needing replacement of their nickel-metal hydride (NiMH) batteries. The only problem even at the end of their battery pack service life was a low voltage reading.The cars have been in service since September, 2005, and Bounds has ordered another 8 to bring his fleet total to 40.

According to Toyota Australia's manager of hybrid sales and fleet strategy Vic Johnston, the use seen in the highest-mileage car during those three years equates to roughly 36 years of normal road use. The math works out a bit differently across the pond in the U.S., with a 15,000mi per year average equating to roughly 16 years of use. Still, that's impressive for a hybrid, and in fact equal to or better than a person might expect of trouble-free service from a similarly priced standard combustion-powered car's engine.