That’s a difficult one to answer as per previous replies. My time ‘at the plot’ varies on the seasons. I often feel I don’t spend enough time there, hubby thinks I spend too much time there.
I go twice a day as a minimum because I have chickens so that’s at least half an hour everyday, & I walk round it at least once on one those visits ,checking on things & harvesting what needs it or what I want for the days meals. As of last year I’ve got a 14 x25ft poly tunnel, so in the summer that takes an hour to water it or 2 of us 1/2 an hour. I do no dig so I spend time making compost. But that spreads out very quickly & saves me spending time weeding. On average I probably spend at least 15 hours a week doing gardening related tasks, be it sowing,planting, soil preparation,harvesting. With build8ng & maintenance tasks on top of that & work in the garden in addition.