In general, your reward should have three components:
Small rewards after overcoming cravings
Medium rewards for each smoke free day
Large rewards for achieving smoke free weeks, milestones or getting through difficult situations smoke free.
You should reward yourself as long as it keeps you motivated. As you get more comfortable in your quit, you may find you are rewarding yourself less and less. That's ok. Just try to keep in mind to re-incorporate your reward system should an urge to smoke creep up.
Faryal - Health Educator