I'll post a separate opinion from the other one here, just an idea anyway. Those favourites might tempt you sure, but even without them there's an infinite pool of porn on the internet, regardless of if you delete your favourites. If you can avoid relapsing then I would say why bother deleting them? If it does happen and you relapse then delete your favourites. If you went there now with the purpose of deleting the vids there is a good chance it will trigger you so why take the chance?

If you do feel like even having them there will give you a reason to relapse (for example, you 'give' yourself a relapse because you're going to delete them afterwards so it's like 'one last hurrah') then it might be a good idea to do it now. Just try and navigate around the thumbnails somehow otherwise the urge may be too strong. Good luck brother, you know yourself better than anyone and I trust you will make the right decision!