6-8 weeks @25mg/day is typical
I'm starting mine off @17.5mg to see if I notice gains from it. Also some people have reported diminishing returns from a constant dose after 8weeks, thats why I'm starting low and will probably bump it up after 5weeks in hopes of seeing gains for 8+ weeks. But I wouldn't recommend running @25mg/day for 6weeks and then bumping it up there after especially for your first run.
Keep the doses on the small side, gradually work up to your sweet spot, and ride that dose for 6weeks. Mk is so mild that 8week cycles are relatively harmless, especially when compared to most pro hormones but a light post cycle therapy (pct) of a test booster/AI combo should be run