So far I get mixed results when playing with cap sense but I can tell you that how long it takes to sense is a matter of how long it takes to bleed the cap through the resistor, the higher the value of those two the longer it takes to bleed. You have with resistor-capacitor setup what is called the time constant, R x C (resistance times capacitance) which I find a little funny with cap sense since changing C is how it works and yet time 'constant'... oh well, it's probably a geek thing.
Here is the most minimal cap sense I know of. It works but I wouldn't use it as is outside of test.
http://arduino.cc/playground/Code/CapacitiveSensor