@Nabzter do you find the smoke is done at 70 days?
None mephisto runs take me 80-85 days.
As said it really depends how you like the smoke, also your environment plays a huge roll. For me I generally i like leaving them longer 80 days plus for a more couchy high but anyone who likes a pure heady high an earlier chop would be ideal.
I have once had a plant finish under 50 days and others over 100. But I have found that all the Mephisto strains could have been chopped around day 70 depending on the buzz you want.