I have a 03 Acura MDX(132K miles) with the V6 and have always changed at 4K miles or less. The last 50K miles, I have always used a syn oil(Mobil 1, Ultra, Edge and I do not see any varnish inside the oil fill hole.
I keep my wifes vehicles a long time and always figured that spending a little extra on oil changes/all fluids, etc will cut down the chance of any mechanical issues. Also, doing a few highway drives a week also helps. Pay me now or pay me later, right guys....