I still have some older alts with capped slayer areas kills.
Back when the level cap was going up to 16 many players set up wilderness areas prior to the new cap ... within 50 or so kills on Orchard and Desert tops ends. When the vale was released people went from level 14 (the prior cap) to the new cap 16 within minutes.
Oh, btw ask any old vet what the significance of the first threnal giant was.