1 doesn't usually light my scene up well... I have used maybe 1 diffuse, with 1 specular off to the side or as a "rim" light and a shadow light, but that's usually for artistic renders where I'm not worried about extreme details...

but for promos or showing off stuff I made I use quite a few lights with different settings to bring out the best quality lol...

I like doing big renders, like usually from 1600x2000 all the way up to 3400x4000 lol, some smaller if it's just a quick render but I normally go for a walk or hang out with friends or sleep while it's rendering lol... XD

If render time is a problem I can size the texture, bump, spec and trans maps down a bit and also try a render with less lights to see if it will render faster with less extreme lights and smaller resolutions, lol.