OK. He's done it. So who's next?
When Hank Aaron retired in 1976 with 755 home runs, the No. 2 home-run hitter among active players was Willie McCovey, with 465 homers ... and McCovey was nearly 40 years old. So Aaron's record looked safe for quite some time, and it was; it would be another 26 years before another player (Barry Bonds, of course) would reach 600 home runs, let alone 755.
Babe Ruth's record lasted roughly 40 years, and Aaron's roughly 30 years ... but what about Bonds' record? How long will it last? To even begin to answer that question, we have to answer two others: