The switching device needs to be suitable to support energy-saving lamps.
I've got three around my property using IP65 Steinel Dusk-Dawn PIRs (so switch more frequently). These devices are suitable for CFLs, which I've got in standard IP66 platic bulkheads (metal light fittings outside no good near us as we're on the coast), and in 2 years, have only had to replace the CFL in the bulkhead over the garage side door, probably because this door slams shut and the mechanical vibration damages the lamp. Of course, the lamps have been operating well outside their temperature range, as we've had a few -10 degree C nights too.
EUR ING Graham Kenyon CEng MIET TechIOSH
Principal and Proprietor,
G Kenyon Technology