The stock firmware does clear the bed level correction matrix when a G28 Home is executed. At that point, Z=0 is the effectively the top of the wiper pad (not the bed). So even if your bed were perfectly level, you really couldn’t print until doing a G29 (or using a big negative Z-offset).
There is a version of the Marlin 1.1 RC3 code available, customized for the Mini by forum member jrhubott. It includes code in the G29 routine that saves the matrix to EEPROM. The G28 routine has code that reloads the last matrix. There is also “off-bed” logic that makes sure the wiper script uses the normal G28 uncorrected Z position (where top of wiper is Z=0, as measured from Z-Max) rather than the G29 probe coordinates (where the bed is Z=0 as compensated from the washer contacts). NOTE: Technically, with stock or this firmware, after G29 the surface of the bed is typically at about Z=0.07 due to the M851 z probe compensation value. That value typically has a negative value of slightly more magnitude than washer thickness, to ensure some “squish” in the first layer. Don’t ever go to Z=0 after G29, or you will run the nozzle into the bed!
So in theory, with that firmware and assuming you are comfortable that your bed plane hasn’t physically changed, you can skip G29’s (after the initial one), go straight to G28, and be using the last G29 matrix.
I haven’t tried that firmware, and some problems have been reported by those who have. You can find more (and perhaps query people who have actually used it) here: