I used to mow 8 acres in 6 hours using a Grasshopper zero-turn with a 52" cut, big Kubota diesel engine. It was a great mower and very comfortable for me to ride (I am a 5' tall 115-lb woman).
There were several areas to mow - two areas that had a lot of shrubs and flower beds to negotiate around, areas with had a lot of mature trees, one open area that had a large slope, a lot of fencelines to mow along, and one larger field of about 2-3 acres.
