First these were second party bulbs. This was our second set from the same vendor, the first worked without issue, lasted as long or longer than the factory bulbs.
We use a liter of ink about every 6-8 months, depending on what I have to print, so you can see that it is not high volume turnover. And, since we have to buy 2 liters at a time, it is not fresh shelf stock. When Advantage carried the ink, before Agfa bought out Pitman, we could buy a liter at a time, and I usually did not keep it on the shelf, knowing the track record of how long one would last, I'd usually order a liter about a month before I needed it.
At least that was until I had a job of printing 48x96 panels with brick wall on them, that burned through a liter of magenta in about 4 days!
Ken