Kombucha isn't supposed to be exposed to light. I wrap my brewing jars with a towel & rubber bands. I'm not sure if it really makes a difference or not.
When I make a 3 quart batch I wait about 9 days, for a 1.5 quart batch I wait about 7 days. But it is all a matter of preference. Every batch is a little different unless you have perfect temperature control. If the kombucha seems week, I let the next batch brew for a little longer. As long as you brew forms a good SCOBY it should be ready to sample.