Thrive on Chaos

Every 25 Fury gained while Wrath of the Berserker is active adds 1 second to the duration of the effect  Diablo III gold.

In order to keep WotB up, you not only need to generate enough fury, but also be able to spend some of it, when you cap it. Sitting at max fury means there's no room to generate more = WotB loses duration.

You need to use your fury spenders and this often means also BR, eventhough it doesn't need to be refreshed. For example a WW barb often buy Diablo 3 items times spams Sprint and BR while holding down the WW button (3 fury spenders).
The goal is to be bellow max fury, not lower than half (depending on max amount).

At other times you might find yourself fury starved.
Limit the usage of fury spenders and/or switch to a fury generator untill at comfortable amount . Fury starvation might lead to WotB expiring, not having fury for sprint between monsters and lowered dps.

WW barbs might find themselves in a situation where not enough enemies are present (for example golden elite mob alone left alive) and WotB is losing its duration when whirlwinding. If you finish the monster by using bash Diablo 3 account buy , while repeadedly pressing sprint + BR, you will gain WotB dura, kill it with high amount of fury left for sprinting to other packs.

Sometimes it might be helpful to stop using WW, but sprinting and lettign the tornados generate a comfortable amount of fury, then continue WWing.

Tip: Attacking breakable objects with your fury generator attack is a good way to get some fury when no enemies are around. Some objects are not clickable/targetable (tables etc), but can be still broken by holding the shift key + attack.