This isn't answering your question, but, when our HIR2 Optiwhites failed (after little over a year), they both went out on the same journey. Interestingly, the Halfords superstore nearby had none in stock.
A few days ago, I had some Osram upgrade bulbs in another car (H7, but anyway...), they were fitted as a pair and they failed within a few seconds of each other. If I hadn't been there to witness this then I would barely have believed that it could happen, but that car has a bulb-fail warning system that is completely dependable, so you know of a failure the moment it happens.
If you are using upgraded bulbs then I would suggest carrying some spares.
Although some owners would argue that it is difficult to tell if HIR2 headlamps are actually on or not, unless you get out the car and stand directly facing them. (For night driving with any confidence someone suggested taking a clairvoyant in the car with you, or only driving under clear skies with a full moon, although this isn't mentioned in the owner's handbook on the Auris).
Only joking, of course.
Also, even new standard bulbs will likely be brighter than old standard bulbs, as the light output drops with age and the technology has improved marginally since they were launched. We have two Aurises with standard bulbs, but the one with the newest bulbs is noticeably whiter and brighter than the one running with the originals.