Welcome! You're in the right place!
I can only answer this based on my experience. Between ages 18-26, I was a 2xPMO/day/everyday guy for 8 years. I would literally go to sleep late doing... well you guessed it... and then have another session in the morning...
During the last 1-2 years of those 8 years, my penis was literally a baby carrot. It was like jelly and did NOT get hard at all. I literally bruised and injured it big time! Yes, I definitely used a "death grip" on it. And yet, while it was wicked sore due to all the frequent "sessions", I still went right ahead and did sessions through the soreness. Also to give you an idea of how deep bad I was in this addition, I had a secret word doc on my computer, over 10+ pages of URLs (single spaced). I literally would have 20 tabs open at once, and nothing got me "excited" anymore... I got to a point where I thought I have seen literally every video out there... and yet, my "thing" was a dead baby carrot, nonexistent erection, and only got as hard as jelly...
It was after I discovered this site and watched the TedTalk "Your Brain on P" when I decided that I want to quit. In my first attempt, I managed to go 49 days PMO/P/MO free. I swear, within two weeks, my erections returned like never before. I literally forgot what it was like to have one... and I didn't even realize I was bigger.
There was a moment during those last two years where I thought "I have killed it permanently"... I thought I would never be able to get it back. Boy, I was wrong.
That said, I did have some "dry spells" with my erections. There are times when days, weeks would go by and I didn't have erections. This is because with PMO still fresh in your mind, you are still in the whole "rebooting" process. Not to mention, I have relapsed here and there... and that stuff has put a huge dent on my progress, especially when it came to fixing my "thing". Even "just one little peak" at a video, would make my erections non-existent for days.
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I don't wanna tell you a hard timeline of when and what to expect, because every guy is different. I have worked with guys who have taken longer to "reboot". I can tell you that it IS possible to fix. I am sure you didn't ruin it for life. I know you can fix it.
According to your profile, you are 24. I am 33, and I only begun my NF journey at 26. I honestly envy you for discovering NF at an earlier age than I have. But hey, if I can make a comeback (though not a perfect one), I know you can too!!!
Put up all the fight against PMO, because it is worth it! If you ever wished your thing was bigger, quitting PMO will do wonders.
Trust me kid, it's not too late!