I'll keep somewhat up to speed with professors that were impactful to me during undergrad, and offer to take them out for a coffee if I'm in their city. It alwa

I'll keep somewhat up to speed with professors that were impactful to me during undergrad, and offer to take them out for a coffee if I'm in their city. It always surprises me how little effort you need to exert to stay on someone's good side. Soft skills will always win.