A method includes reading a group of analog memory cells using first explicit read thresholds, to produce first readout results. The group is re-read using second explicit read thresholds, to produce second readout results. The group is read using one or more sets of auxiliary thresholds so as to produce auxiliary readout results, such that the number of the auxiliary thresholds in each set is the same as the number of the first explicit read thresholds and the same as the number of the second explicit read thresholds. A readout performance of third read thresholds, which include at least one of the first explicit read thresholds and at least one of the second explicit read thresholds, is evaluated using the first, second and auxiliary readout results.