fwiw, the PJRC server has the last 64 releases, going all the way back to version 0.95.
The very early versions were removed when Cypress Semiconductor (now acquired by Infineon) was threatening trademark infringement against anyone hosting a certain Arduino library (which was first published before they filed for their "CapSense" trademark).
The beta test files are usually deleted after a couple releases. Until recently the PJRC website was hosted on a server with 80 GB, which didn't provide enough space to keep lots of beta software installers. Today we're on a new server with 480 GB. But after each stable release nobody downloads the betas that led up to it, so unlikely they'll be kept.