When I worked for myself (15years) I always batch baked… I would prep all my tins and then with fruit cakes I would mix batter and add to large bowls full of prepared fruit mix. Then would fill my tins and and bake over a weekend with no problems.. Using up to 80 lb of fruit.
With sponge cakes I would prep my tins and continually mix for up to ( think the maximum I prepped was for 18 cakes) As soon as one lot out of the oven I would put more in until they were all baked. Over a day without any problem. 😊