My shaves tend to take a fairly long time, including all the lather building, shaving passes, and clean up.
One negative aspect of things taking time is that the quality of my lather decreases over time. When I whip up what I think is a nice lather, the first time I lather up is really nice. The second time is good. The third time is so-so, and the fourth time is kinda 'ugh.'
I think I still have a decent quantity of lather available on for my fourth pass, but the quality of it just isn't there. It seems too thin, but it's not really bubbly or anything like that. I'm not sure what I can do to revive it. More water?
I've had the same problem with Proraso cream and with a glycerine-based soap.