Brake pads at 40k, dealer says replace now, indie says I've got time

[phineasfogg]

Had my Q3 in for its regular service and the dealer flagged that my front pads are at 3mm and told me it's urgent, must replace immediately, safety issue, the whole speech. I get that 3mm isn't great but I've done maybe 40k km which feels early for pads to be done, and the car brakes perfectly fine, no squealing, no grinding, no warning light. Took it to another place just to sanity check and the guy there said I could easily get another few thousand km out of them and there's no rush, which is the complete opposite advice. So now I'm stuck in the middle not knowing who to believe, and wondering if the dealer is just padding the bill or if the indie is being too relaxed about safety. I did a bit of digging online to find out more about when pads actually need changing versus when it's just a recommendation, and it seems like there's a lot of conflicting info out there. Anyone know what the real minimum thickness is before it becomes genuinely unsafe? And does driving style make that much difference, because I do mostly city driving with a lot of stop start which I assume wears them faster. Also should I replace rotors at the same time or is that another upsell?