That is an extraordinarily interesting question and that suggests I haven't got a very good answer to it. You're probably well ahead of us on this. The case of paper petitions...for example, I did a paper petition a few years ago and got 16,000 signatures. We put that in the bag behind the Speaker's chair and that paper petition is kept indefinitely in some vault for hundreds and hundreds of years.
Obviously, computer systems are governed by data protection, but I think you've asked a very good question and I'm embarrassed to say we haven't thought that far ahead. My assumption was and is that these signatures would be retained in the same way that paper petitions are kept, so as a source of potential historical interest.
But Huw may want to come in on this.