I agree, I don't think you should stress the amount of time you spend just yet. Speed and accuracy will come with lots of practice. For now, just go at your own pace and take your time to make nice shapes. Something that helps me -- and you did it in some places here -- is to imagine a wireframe over the object. This helps me to determine the planes that are facing towards and away from the light source. I can use this to plan my values. In your drawing, there is a high contrast between the light and dark values, so incorporating more half tone value shapes will help add volume to those bananas. Hope this helps!