DATA is used to store the value(s) in the EEPROM when the device is programmed. Ie. to get a "default" value in there. It's embedded in the .hex file image which get programmed into the device.
WRITE is used to store values in EEPROM during runtime.
It doesn't matter HOW the values got there, READ will access them.

You don't really have to keep track of the adresses etc, you can do
Ch1_On_Time DATA WORD 1234
Ch1_Of_Time DATA WORD 2345

This way you have created a label for each entry in the EEPROM which you can then use when your READ or WRITE from/to it in your code. Please note that Ch1_On_Time in this case is NOT your variable - it's ONLY a label. To actually USE it in your program you need to READ it from EEPROM and Place it an ordinary variable - but you're already doing that.

Using arrays, the EXT modifer, and indexing thru the data as in Richards example is probably more efficient code wise but may not be the easiest way to debug and/or understand. YMMV.

/Henrik.