For Sale: Fizik Gobi Saddle, BLT Ozone Light

The batteries do not look to be that cheap- how long does one set last?

From www.battery-force.co.uk :
In this box of six, the Energizer CR123A battery is superb value. And because our stock is fresh, any spare batteries you buy will work for years to come.
Find all batteries of this type
Pack Information
Batteries per Pack: 6
Data Sheet: Energizer product datasheets
Mfr Part Number: 628290
Pack Contents: 6 x Energizer CR123A Pack of 1

Pack Weight: 145.0g
RRP: £41.94

that's pricey... I bought some Duracells from Waitrose the other day for £2.50 each.