Been playing since July 2018 and have fully ascended 22 5* heroes with the mats for another 3 waiting to see what I pull on this next Valhalla before deciding which heroes to ascend. Once I use up those mats, I’ll have at least 4 of each remaining while I wait on 4 to 6 of each of the other 4* materials to accumulate for additional ascensions.
I guess I’ve been more fortunate with collecting these as I have collected 29 of each in a little less than 2-1/2 years.