Olanzapine has a mean half life of 30 hours (but up to 50 hours). Rule of thumb for eradication from body is 5-7 times the half life.
Therefore, give or take, call it 180 hours to clear (6 x 30 hours) - that’s a smidge over 7 days to be clear of it.
On the plus side the long half life means withdrawal effects may be minimal as You stop.
I’ve found anti-psychotics greatly interfere with IV meth. In my case the calculation for eradication of Abilify was 14 days but it was only at about 21 days off it I started to really get bang for my meth buck.
However You might find taking the olanzapine for 2-3 days again at the end of your high both mitigates the comedown and reduces neurotoxicity. This seems to be the case with seroquel and abilify in my experience.