I’m x years old is it too late to learn service design?
In short: No. You're never too old to learn something new. So you are definitely not too old to learn Service Design.
That's especially true as Service Design is a practice that complements everything you already do well. Learning Service Design doesn't force you to change careers. Instead, Service Design can give you additional tools and perspectives to bring to the job you already have.
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What are the mental health challenges a service designer will be faced with?
In short: learn to deal with negative feedback, give enough time for life and learning, keep track of the good stuff, and don't forget to sleep.
Can a service designer survive a recession?
In short: Yes, if you can also provide a lean and low-hanging fruit approach that is focused on the present. No, if you are "only" focused on long-term strategic work.
What are tips to become a senior service designer?
In short: mentor others, teach others, try out new technics.