How often should I be rechecked after being diagnosed with ic?

Depends. It depends on the treatment employed, your symptoms and your progress. If you are stable and tolerate the treatment well, you may need to be checked every 3-6 months. If the treatment is ineffective and you get frequent flare ups, you may need to be seen monthly or ever more frequently.
Depends on symptoms. Ic is a chronic problem. If you learn to recognize the symptoms and identify the triggers that make it worse, you don't have to be seen a lot. If you are learning about the symptoms and dietary triggers, you will need more frequent appointments for symptom relief and further education by your physician.