Never. When the next WHQL driver comes out (probably not this month), it will be numbered after the year.month sematic as usual. So if it comes in september, it'll be 13.9. If it comes in december, it'll be 13.12 etc.
Why are you afraid of non-WHQL drivers? They work the same way, you only get a warning from the OS when you install the package. That's all.
CPU: AMD Phenom II X4 810 @ 3120MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 835/1135MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 3.11 Pro x64