Shortly after Gravis had said that he was ready for his tribulation, a tribulation token was deployed in The Heaven Company.
People that were willing to undergo their tribulation earlier than planned could request a tribulation from Heaven. Heaven was always listening.
However, there were some caveats.
First of all, the longevity gained after undergoing the tribulation earlier than planned wasn't additive. It simply put the current longevity at the maximum for the Realm the person was at.
Second, one could only request a tribulation if less than 10% of the maximum longevity of the current Realm were remaining. This was to stop people from just getting tempering whenever they wanted. Otherwise, people would just vanish from the face of the world and reach the peak without leaving their homes.