I suggest submit frequently.
auto-submit isn't necessarily a good option. You can make some accidental updates and those will get auto-submitted. This will turn out to be a disaster.
Better than frequent submissions is to keep a note of your answers in a paper. If you lose the page anytime in between, you'll be able to quickly re-enter all your answers... You also have a better sense of how many are done, than having to scan through the entire page.