In Hack’n Slash Diablo 3 , Blizzard warns players now about losing items.
Blizzard warns in a letter to the players of Diablo 3: Those who have used the reincarnation to Season 5 should secure their loot from the past. Because we soon have the 30th day of the new season and then the earlier loot of the reincarnated characters will expire.
Because the “old” items were taken from the heroes and then sent to the non-seasonal characters. And only within 30 days can these items be claimed, otherwise they are lost.
For all further information, you can read it here directly in German from Blizzard.