Leaving wifi on can cause battery loss as mentioned as it will scan for available networks which uses power.
I would just long press on a blank part of your screen add widget then choose the power control widget. You can then control wifi, bluetooth, gps and screen brightness with a single tap to turn off or on.
If you want something similar but more customizable you could try widgetsoid and create custom widgets for shortcuts, power control (bt, gps, work etc) and change colors, transparency, icons etc.