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My FLI ML8300 developed one that disappears around -5C and I usually operate it at either -35 or -40C where it is absolutely perfect.
You are right - its hot pixels that get dragged along in the readout process. When I bought it it did not have any. I guess it appeared about 2.5 years later. Perhaps earlier as I don't normally view the chip until its chilled and it does not show then.
KAF16803 chips often have a couple. Mine had none and developed one after 1.5 years. CCD chips also age from radiation damage and could develop a line like this at any time.
Then it becomes a matter of how many is acceptable? Ideally you would have none but that is not the real world of CCD chips.
If you make sure your darks are fairly recent or updated especially if one appears it should dark subtract out if you combine enough darks and make sure they are at the same temperature.
Greg.
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