Various Thoughts:
This deep into the thread and no one has mention Bob is the Oil Guy website yet.
I tend to follow the owner's manuals for my vehicles, and change the oil, etc, as they recommend. I think they are very conservative and you could go a lot longer between changes, but I tend to be pretty conservative myself.
I am no expert, but I have always read that you can't tell much about the condition of your oil by how dark it is. See the Oil Guy website for more. Of course, if your oil looks milky, it may have water in it. (Or may be contaminated with something else). So it doesn't hurt to do a visual check and do it often. Naturally, you will want to keep it topped up.
I think it is foolish to pay a lot for oil then scrimp on the filter. Either scrimp on everything or scrimp on nothing.
Dino oils are probably plenty good for most cars, depending on how they are driven. Again, let the factory owner's manual guide you on this. For most of us, synthetics are probably overkill.