Well, it seems to last about the same as the original battery that I used for a year and a half. Which means I have to put it on a charger every other night or it will day before the next night. When my tablet was new (and I was really hammering the usage back then), I could normally go 3 or 4 days between charges.
Newegg just got back to me with this:
So, they are saying that Samsung made all the replacement batteries for these tablets back when they manufactured the tablets themselves and they are not making new batteries for it any more. Effing LAME!