I think it's random (Destiny)

by Xenos , Shores of Time, Monday, July 13, 2015, 22:30 (3520 days ago) @ DiscipleN2k

I had one ready in 24 hours, but the 2nd one took 72. I'm hoping this doesn't mean that when I get my 3rd that it'll take a full week to be ready :)

-Disciple

Nah, it's random between 24 and 72 hours. Second one took 48 hours for me.