The "resume later" option could work here.
But honestly, I would go for a different approach, but this also depends a lot on what you are actually trying to set up.
I would give each of them an ID, create various surveys and send those surveys out to them when it is about time to fill the next part. I think a lot of people forget about the survey, lose the link, etc. So you'll have to sent a reminder anyway. With the ID you can later join results for analysis purposes.
This has also a psychological aspect: people like it when they managed to finish something. So it is generally better to have several short surveys over time than one big one. Another advantage is that you have already finalized results for the first surveys and could start analysis based on this and eventually adapt the following surveys accordingly.
However, as I said, if this is a solution for you depends of course very much on what you pretend to do.