invite coffee chat after the final interview

I was interviewing online for a new job oppotunity with a company. It was held 3 times with interviews consisting of various employee. I was informed by the hiring manager that I had passed the final interview. However, after the final interview, the hiring manager requested a casual chat at a coffee shop near the company. This casual coffee chat was an opportunity to chat once again offline over coffee with the employee who handled the online interviews. It is still going on and there is no end in sight. Is this a common occurrence in the job interview process? This hiring process has been going on for over 3 months, although the hiring mamager has suggested that there are other candidates for this position so the company wants to assess each candidates personality.