How long did it take to create these exploits?

If Ur gonna use an API it depends on how much effort you put into the UI and other functions

creating the perfect ui is the hardest part for me since you don't exactly know peoples expectation compared to yourselff. for me i personally dislike a more minimalistic approach many exploit devs took and i prefer sticking to older designs

if you go up and maintain your own dll, it's no longer a matter of how long it takes to make it. it's how long until you will get frustrated with constantly maintaining your dll especially when roblox releases big bad update

however asking how long it takes is an invalid question to ask. jjsploit and krnl are both in constant development and maintenance, improving from user feedback or whatever. again, it's really how long you are willing to do this for.

the reality is that even big exploits will eventually meet its fall due to devs simply focusing on something like school.