Typically in asphalt you can cut out a manhole in 8-12 minutes or about one minute per inch of cutting depth. In concrete it will be more like one and a half minutes per inch of depth. In harder concrete it's up in the air on time of cut and some aggregates are almost impossible to cut.

Resource Link: https://mrmanhole.com/rebuild-method-for-manhole-repair/
Additional Link: https://www.youtube.com/watch?v=rcGaOI5QyfY