I am interested in this, but have read mixed reviews to do it or not. My main lense is 18-140, I don't have any set things I shoot, just random stuff, mostly off a tripod, would I benefit from fine tuning?
It depends. The way Nikon has implemented the focus tuning is not perfect. I have tried the feature in the past but my results were never good. The problem is, lenses typically require different focus tuning parameters depending on the focusing distance, but we can only enter one value. If you have a 50mm f/1.4 prime lens, that needs +5 at 1 meter, -7 at 5 meters and +3 at 30 meters and beyond, which number will you enter?
And the thing only gets worse if you have a zoom lens. You would need 3-5 different zoom settings and 3-5 focusing distances for each zoom setting, yielding 25 fine tune values. Which one will you pick?
I have 5 cameras that allow focus tuning (D300, D3S, D3X, D4S and D5) but I have not done it. Maybe I am lucky or just blind, but none of my lenses require FT. On the other hand I only have Nikkor lenses which all perform beyond my expectations *knock on wood*.
One thing to remember, the FT should be done in bright daylight, if you shoot in daylight. Tungsten or fluorescent lighting cause focusing error (not large, but perceptible). Or vice versa, if you only shoot in tungsten, then tune in tungsten.