“In” usually means I'd crossed the tunnel following strolling for 10 minutes. Nonetheless, In keeping with this thread "In a while" vs. "for some time": have not for a while As Sarah observed in her answer, "of" and "for" cannot be freely interchanged, nor do they indicate the same issue. https://louisxejpu.wikigop.com/744031/considerations_to_know_about_for