There have been quite a few patients on this forum who say they experienced less pain when they did 0.75 mm instead of 1mm per day. But I've only seen that in the Tibia diaries. About femurs, I have only seen diaries citing 1mm per day.
It makes sense that your recovery will be of a better quality (I don't want to use the word faster, because there's no evidence) if you lengthen at a slower rate, because you're taxing your soft tissue and muscles less.
As for the risk of pre-consolidation, if you're worried about that, you could ask your doctor to review your X rays once every 5-6 days during the initial days of lengthening so you can see how fast/slow your bones are consolidating, based on which you can decide on rethinking the rate of lengthening.
Another important thing to consider is: If you want to lengthen large amounts like 7.5 or 8 cms, are you really willing to wait (75mm/0.75 mm per day) 100 days to finish the lengthening phase?
Dr. Paley, I believe, from some of the diaries, speaks about a breaking point in the lengthening phase beyond which the muscles & soft tissue "give in" to the lengthening. You could possibly speak to your doctor about lengthening 0.75 mm per day until you reach this breaking point, lengthening 1 mm per day in the "honeymoon" phase (no lengthening pains) and then slowing down as you come nearer to your goal.
Again, I'm still looking for an answer as to whether the above applies to femurs as well, because I've not read any femur diaries till now where the lengthening was less than 1 mm per day.