User blog comment:Godisme/Everything But The Rain Op. 2 "The Rudiments"/@comment-1393830-20130306172253/@comment-1332195-20130306202125

re: the get together, I'd say Isshin deliberately avoided that so Ichigo didn't learn of his heritage, and if he had appeared, Rangiku and Shiro would hopefully respect him enough to keep it quiet.

As for the aging question, I guess Urahara could make a realistically aging gigai. Or, just like the family car, it gets replaced every few years (for an older looking model). Latter's simpler to do imo.