HR diagram of the stars of Fig. 8 observable in different conditions. The domain where stellar ages can be estimated at the 10%-level after grid-based modeling corresponds to the condition δM/M = 5% obtained from scaling relations. The color denotes the number of stars in bins with ΔT_eff = 100 K and ΔL/L = 20%. The dotted line shows the red edge of the instability strip; the dashed lines show the limit between the short- and long-cadence acquisition mode of PLATO, for 1 or 2 M_⊙.