Board Thread:Manga Discussion/@comment-5967049-20150219202823/@comment-87.113.107.203-20150226183929

Personally, I just think it was the cost of him mastering his time stop ability, like how Dio was defeated by Jotaro because The World wasn't as durable as Star Platinum, perhaps to make up for its greater range (10m vs. 2m) and longer time-stop.

I mean, in Part 4, Jotaro could only stop time for 1 or 2 seconds, due to (paraphrasing) "having not used time-stop in almost 10 years". Perhaps the events with Kira and the other malevolent Stand users in Morioh changed his mind about slacking off, especially wiht his age, and he honed his time stop abilities (I'd argue Araki just decided to retcon 'Star Platinum' as 'Star Platinum: The World' post-Part 3).

The reason why Jotaro's Star Platinum (as well as the second Diego's The World in Part 7)'s durability was weakened was probably becuase it takes a lot of energy for a human to withstand stopped time for even as long as 5 seconds, whereas Dio - an immortal vampire who had "transcended humanity" and survived for a century in a coffin without any sustenace - would've eventually been able to consecutively stop time as long as he liked, if he hadn't died after reaching 10 or 11 seconds.