First of all, I just wanted to add a "success story" for GTN. It healed my fissures in less than 2 weeks. I used the 0.2% strength and had a killer headache the very first time I used it but then nothing since.

Just wondered if I should keep using the GTN for a few weeks / months to try to be 100% sure I am healed. What do people think? I'm terrified of re-tearing it and starting from scratch.

Personally i've been using diltiazem for more than 8 weeks just when i need to though, so after bm's and and if late night my bum gets achy i'll add some but I wouldn't say I'm healed 100% as i still watch my diet v closely and feel some pain after a bm but I'm definitely not feeling the same stabbing pains i was 5-6 months ago,
just be mindful of your body but don't feel like your just as new, follow the same diet rules and use GTN after bm's
Keep the bm's as soft as humanily possible and you'll be lit