Works really well, it saves me a lot of time I would otherwise waste with scrolling through YouTube or Reddit!

I have noticed that it is very easy to access the blocked sites by disabling the Addon from the addons page, which takes only a few clicks. This is probably not changeable from the extension code (to prevent bloatware extensions from blocking their removal), however, you can lock the extension yourself using the Firefox policy system, which prevents removal https://support.mozilla.org/en-US/kb/customizing-firefox-using-policiesjson

For reference, this is what I put into my policies.json:

{
"policies": {
"Extensions": {
"Locked": ["leechblockng@proginosko.com"]
},
"ExtensionSettings": {
"leechblockng@proginosko.com": {
"installation_mode": "force_installed",
"install_url": "https://addons.mozilla.org/firefox/downloads/latest/leechblock-ng/latest.xpi"
}
}
}
}

This way, you have to remove the file and restart firefox, for me this is cumbersome enough to stop me from disabling the extension.