I've run the stock seat and the Sargent's Seat on my Super10, and finally took delivery of my long-awaited Russell Day-Long about three weeks ago.
The stock seat, for me, was good for 60 miles until discomfort, 100 miles until serious discomfort, and 200 miles until pain that didn't go away overnight. The Sargent seat basically doubled that or better, but it was still not suited for days longer than 600-700 miles. The Day-Long is, as always, the best option for when comfort trumps all other considerations. I've ridden 1800 miles in 24 hours on a Day-Long (on a different bike) during the '99 IBR, and over 25K miles in a single month on one - all without ever feeling like my fanny was a limiting factor in my riding. I won't ride long distance without one.
FWIW - I've had zero luck in using gel covers or gel inserts (too temperature sensitive, too ill-contoured to the shape of my fanny), sheepskins (only useful to avoid chafing), or beaded covers (man, they just hurt my butt). They are all band-aids to the problem, and not a true solution.