I made two test simulations using AWI-CM3 (with TCO95L91), with different values of GGAUSSB (gravity wave flux parameterisation). Increasing the period, the easterly component becomes weaker, but the QBO activity is not getting weaker with time as shown in previous cases, it also does not markedly modify the general climate in the simulation
The performance indices are computed for all the three experiment with respect to CMIP6 (period 1980-2009) in the top row and for the two experiment with increased QBO period with respect to the simulation with annual QBO period in the bottom row.