I have taken my car to a dealer and a auto mechanic body shop. The shop replaced my breaks in sepetember of this past year. Went to get work done at the dealer regular maintenance and he said my breaks were at 5mm. But the shop says they still look brand new.
The standard thickness of just about all new brake pads is around 10mm. If your brake pads are at 5mm, they have about half of their usable life left. I would recommend replacing your brake pads when they reach a thickness of around 2-3mm. Consider YourMechanic for your next brake pad replacement as it can be completed at your home or office.