This is why I as an autistic never usually propose ideas how do you delete posts
no need to delete your postings here, Natterjack. As for your question about safely ending a dig when the focus has run out ... try simply backing away from it. I think that then your focus does yet auto-refill to its max. I also suggest trying to switch to only stabilizing and / or both stabilizing and preserving, in other words to toggle the way you careplan, then also stepping away.
all of the above (i may be wrong, but i think it works that way) should pretty close to immediately end the time out of the dig, so that you can begin a new source with full focus complement.
Hope i am right and also this answere (correctly) your question. Sorry that i did not before now notice and then get to therefore take the time needed to answer your post.