I had my interview at the Dallas DO today May 14th. It went very well. I was very nervous about my extensive travel over the past 5 years. I had some 800 odd days of travel that included trips to a lot of countries in the world. But none of my trips was over 6 months, the maximum trip length was 110 days. I was working for a US company as a contractor and did have a letter from the company for the reason for the numerous visits.
When an I-485 is accepted at the Service Center, requests for FD-258 FBI fingerprint checks, fingerprint fees, and G-325A consular background checks are made by USCIS. Responses to these requests come back to USCIS and must be matched up with the appropriate files held in staging. File Maintenance "file connects" these responses to the corresponding files.