Storing config in EEPROM is easy and works in most environments. No need to be Teensy, or even Arduino, but here is my Teensy specific data.

#include <EEPROMex.h>
struct CONFIG {
	byte mode;
	int displayBright;		// -255 .. 255 (negative = inverse)
	unsigned long test;
	unsigned int displayInterval;	// How often to update display params?
	unsigned int environmentReadInterval;	// Read Temperature / Humidity
	unsigned int environmentLogInterval;	// Log / Display temperature / humidity
};
CONFIG config = { 0, 0, 0, 0, 0 };	// You can set defaults...

void setup() {
	EEPROM.setMemPool(0, 2048);  // EEPROMex did not know Teensy 3.1 default EEPROM size
	readConfig();

	// Display current
	Serial.print("Config test = ");
	Serial.println(config.test);

	// Increment each time starts up
	config.test++;
	writeConfig();
}

void loop() {
}

void readConfig() {
	EEPROM.readBlock( 0, config );
}

void writeConfig() {
	EEPROM.writeBlock( 0, config );
}