We do not currently support incremental analysis as it can result in less accurate scanning results. This has come up quite regularly, especially in the context of branches and pull requests, and internally there is a lot of discussion around this, but I don’t think we have anything to share at this time.
That said, 25 minutes on 160k LOC seems a little long (although that’s not exactly scientific).
- Which side of the analysis is taking so long – the actual scanning or the background task on the SonarQube Server’s side? (If the former, how long is the background task taking to process?)
- What version of SonarQube and relevant plugins are you running?
- Are you using any plugins that run other analysers (PMD, Checkstyle, Findbugs, etc.)? These are often the cause of lengthened analysis tasks and is rather out of our control.
If you have logs to share from analysis, preferably with debug mode enabled, we might be able to do a sanity check. 
Colin