My previous experience with the Fatar TP8O include the Korg CX3, Nord C1, Nord C2, Nord Stage 3 Compact, Doepfer d3m, Viscount Legend Live and none of these have changed character over time. I can not exclude that the springs soften after being broken in but that effect must be really small. My Mojo 61 is from 2017 but very little used. Either the production of soft springs are really inconsistent or they must have put in the wrong version in my Mojo 61B I am afraid.