It all really depends on your goals after a training program is over. For some, they do a program to get stronger for a specific event, others use a program to improve their overall fitness and once the program is over, they go back to their normal riding schedule, just stronger.
I’d recommend that you look at your cycling before the 12 week program started and determine your baseline (could be based on distance, time, power, relative effort, etc.). Then after the 12 week program, set a target for your previous baseline + 10%. After a week or two at +10%, evaluate if you want to bump it up another 10% the following week.
Find the balance where ride and achieve your goals and push yourself further if the rides are feeling too easy. Also note that “having fun, being happy while I ride” is a completely valid goal. It’s not only about speed, power and fitness.
As Greg LeMond said, “it doesn’t get easier, you just get faster” … I’d modify this to say “It doesn’t get easier, you just get faster or have more fun”