Tier 4 extension timelines

I'm planning to apply to extend my existing Tier 4 visa which expires 21.07 and plan to use the standard service to lodge an application by 1st week of May. The Home Office says that it takes up to eight weeks but based on recent experience, does it take less than that? I am planning to travel in June but don't want to waste further money if there's a good chance it could be returned sooner than the eight weeks.

I know there's a page like this: uk-tier-4-student-visas/time-lines-for- ... 48607.html but it was last updated three years ago so I'm not sure what the scoop is now.