Yes, this month was a record one for me. I have sent over 20 000 reports in the last 30 days. I think I have reached some certain internal memory limit (or something like that) and now this page is completely inaccessible to me. Previously, I had never sent such volumes of reports, so everything always worked properly. Recently, the report history page has been taking a very long time to load despite a constantly stable internet connection. I think it's somehow related.
I don't think I have ever exceeded ~10K in a month, so your hypothesis has some credence.
(it's also easier to export and report in chunks for future use)