The neutral print test holds up pretty good while the sepia print shows a little more fading because of the increased use of yellow which is the most problematic of all the Epson inks.
This full set of ABW presets (i.e., "cool", "neutral", "warm", and 'Sepia") on HN photo rag Ultrasmooth plus additional samples tinted to the extreme positions of the ABW color wheel have ID'S 227-236 in the Aardenburg Light fade database. ID# 226 is a full color image also printed on same paper batch and printer at the time the ABW samples were made. As we'd expect for the ABW results, the extreme yellow tinted sample is the one to first reach its AaI&A Conservation Display rating limit (56-59 megalux hours). None of the other samples have reached their limits yet, so testing is ongoing, but the trends already suggest the extreme cyan tinted sample will also do exceptionally well, the magenta and red tinted samples less so. Preset "Sepia" will be weaker than the other ABW preset tints but significantly better than the extreme yellow tinted sample, again a fairly predictable result but good to see demonstrated in practice.
Keeping these ABW tinted sample results in perspective with the full color Epson K3VM sample fading (ID# 226) and also comparing the 56-59 Mlux hour rating of the worst ABW tinted sample (the extreme yellow) to Aardenburg display ratings for other third party monochrome ink sets that are not "full carbon" ink sets, the ABW test results are very respectable. Thus, if you make B&W prints using Epson ABW mode, I wouldn't worry too much about the effect of tinting on lightfastness. I'd worry more about choice of media. An unwise media choice will seriously undermine any B&W print's overall hue stability. Take a look, for example, at ID# 146 which used a full carbon pigment (highly fade resistant) ink set on a paper that exhibited rapid OBA burnout and therefore visually apparent "yellow staining". The magnitude of the media whitepoint shift caused a noticeable shift in hue throughout all the image highlights and many of the mid tone values in this otherwise very stable image printed on that paper. As that overall hue shift occurred, it in turn triggered the very sad 6 megalux hour Aardenburg conservation display rating for this sample!