Use Items instead of global variables. Then you can have just one set of Rules that handles the countdowns for both Timers. It also lets you take advantage of Design Pattern: Associated Items.
Then your code remains generic. Do not repeat code. You will use the name of the Item that triggers the Rule to construct the names of all the associated unbound Items that store the values you need. With the name you can get access to the Items to get their current state and postUpdate or sendCommand to those Items as needed.
Then your Rules code can be left generic and will work for these or any other countdown timer you may want to implement. If you want to add a new countdown timer all you have to do is add a new set of Items and add those Items to the right Groups and you never have to edit the Rules.