I suspect the cause is mostly heat-related. As newer bulbs run much cooler I expect reliability will be better, but the product line is definitely not bullet-proof.
The color bulbs in particular are horribly dim, but fun nonetheless.
The only failure I've encountered in ~10 years is my original Hub started crash looping a few years ago and I ended up getting a new starter kit to replace it. The bulbs seem to really last, however.
What do you mean, do they not produce the advertised number of lumens?
Just looking at specs, their highest output coloured bulb produces 1521 lumens at 4000K white colour temperature and 1055 lumens at 2700K [0].
That's very close to the brightest regular bulb I can find in stores (1600 lm).
[0] - https://www.philips-hue.com/en-gb/p/hue-white-and-colour-amb...
I suppose I have to consider replacing everything now...