I couldn't find any evidence of Porsches having a 60-year full service maintenance agreement. But even if it exists, I guess it would really depend what the agreement contained. I don't think most Porsches are going to be running after 50 years.
I'm no expert, but my understanding is these Siemens service agreements are contractually paid agreements with yearly revenue, and that revenue is based on keeping the train in service and fully operative for that entire time period.
I found another article in which Siemens provides 35 years of full service maintenance for its brand new electric locomotives (sold to a different customer.) So short answer: yes. https://press.siemens.com/global/en/pressrelease/siemens-mob...