During the early spring I built a fiberglass sink to improve my darkroom. I use to work off a 36 inch counter top but found that this was too low for my tastes.
I prefer to stand while doing the wetside and decided to raise my sink to a comfortable height for me. The top lip of my sink (where I rest my arms) is at 43 inches and the sink bottom is at approximately 40 inches.
I also have a stool in the darkroom which I sometimes sit on and the height of the stool works very well with this sink height. I have always felt that standard kitchen and bathroom cabinets are too low for my personal comfort. I believe the standard makes it easier for children and shorter people but does not address the comforts of taller folks and those who do not wish to bend over that much.
Just my opinion and what works for me. Also by raising my sink a bit higher, I now have more storage area below to hold the 20x24 trays and a variety of other things.