After I upgraded to Mac OS Mountain Lion: My MacBook suddenly took much longer to become operational again after I opened its lid...
In terminal or iTerm enter the following:
sudo pmset -a standbydelay 50000
This sets the delay from the default 4200 seconds up to 50.000 (more than 13 hours)
The OS has two different hibernation / sleep modes: one preserves the whole RAM content during sleep (which makes wakeup a breeze), the other stores RAM content on disk or SSD (which, in case of several GByte RAM, will need 10 secs and more to wake).
Thanx to some discussion on apple.stackexchange
In case you want to learn more about hibernation and power management - consult the reference documentation.