Of course Japan's Nikkei index is still well below its peak in 1989. It isn't smart to assume that 7% will continue forever, particularly since developed economies' growth rates have all slowed, and without massive immigration slowed demographic growth makes it unlikely the rates will increase again.

In any case, if you believe your charitable donations are better off invested in the stock market than being put to charitable work today, then why bother donating? That means you don't believe in the charity. It would be better to find a more effective charity!