Regen frequency is based on time, miles, starts, heat cycles and percentage blocked. There is a maximum time dependent as well, which is there for safety in case the other parameters don't compute.
Some peeps think time is the only factor and have produced 'evidence' but all this evidence proves is that something somewhere, a sensor perhaps, isn't working the way the system expects and is mucking up the calculations and the ECU is defaulting to time.
This usually starts a blazing row on here.
The miles I quoted are in the range where most will regen, 180 round town, 350 on the motorway at constant load. You can look at your own cars regen history for an idea.