If you reread the first post, you should note that items that are either duds or from tables A-D are taken into account already. The average PC finds 6 permanent items over the course of 20 levels, 1 of which is either from tables A-D, not particularly effective, or cursed in a permanent way. The other 5 permanent items shift the math in some significant way.
And I wouldn't underestimate how Boots of Speed change encounters - its presence means that a typical party can focus fire any opponent in the first round, regardless of where it is in the room. Unless the room is very big.