When do Polish people use "pan/pani" versus first names?

Hello,

I've been living in Warsaw for 3 months now, and I'm still struggling with when to use formal versus informal address. I get using pan/pani with older people or in formal situations like at the bank, but what about with coworkers? Some use first names right away, others stick with the formal form even after months of working together.

Would love to hear your thoughts!