Starting next month

[Encroaching Death]

Plane of Fear is probably the shortest out of all the early Planes.

Like an hour.

Plane of Hate is probably next.

Plane of Sky probably takes the longest. Clearing all Islands can take 3 hours or so (at a casual pace)

It all depends how far you go with it too.

Sometimes guilds don't feel like/or don't have the opportunity/ability to clear everything, so they may only go to Island 4 in PoS for instance.

It really depends, but I'd say on average maybe 2 or 3 hours.