I've configured my output connector to commit both at the end of a job and "within" 600000 ms (which should be 10 minutes, if my arithmetic is correct).
The effect I'm seeing is that commits are occurring as jobs complete, but if a set of long running jobs aren't completing quickly, I'm not seeing commits every 10 minutes.
FYI, here's my Solr output connection configuration
Use extract update handler=false
Solr core name=OasysMailSearch
Server web application=solr
Maximum document length=10000000
Solr content field name=body
Server update handler=/update
Server status handler=/admin/ping
Server remove handler=/update
Solr id field name=id