Took me, on a 350-400~ ed at the time, around 20h on normal respawn, looping around the Dryad gardens.
At the orange arrow, levitate down to complete the loop. There's 18 total elder forest fury and it took that long because i was doing all bestiaries down ther at the same time. If you focus only on elders, you might be able to cut it down to 10-12h i reckon