Great things are afoot - the first two bulbs from the sample group as featured in this post have gone phut and, indeed, kablooie. And already the results are interesting - it was two of the high-powered incandescent 40W bulbs that went (at roughly the same time, on Monday 5th), as you might expect, but it was two of the new ones rather than two of the old ones that had already been cycled on and off an indeterminate number of times.
If you care to refer to the original bulb layout diagram, it was bulbs 2 and 3 that expired. This is actually quite opportune, in a way, as I just happen to have in my possession two new IKEA LED bulbs which I can now slot into the two gaps that have just opened up.
At first glance they are less blue than I was led (see what I did there?) to believe they might be - they are broadly the same sort of yellowish hue as the incandescent bulbs. Their "colour temperature" rating is 2700K, if you're interested in that sort of thing.
Anyway, now the science bit: the two dead bulbs both lasted a pitiful 6 days each, at a cost of a smidgen under 25p per day. At that rate of attrition the LED bulbs only need to last 16 days to be better value, but I'd hope they might manage a bit longer than that. Time will tell.