hm... hard to say. i think it was something around 800 - 1000 hours maybe. but since then the star rating has been made a bit easier. i think the 5* back then would now be around 5.2 - 5.3*. also there were less farm options and when i first started there was no pp system but score ranking so i didn't even try to improve.
i would say right now i'd probably make it in around 500 hours or so.