...snip...

- There's now more fair build scheduler.  Previously, no matter whether the
  "background" attribute was set or not for the build - once builder was
  allocated for a concrete copr user - copr never terminated the builder
  as long as the user kept filling the build queue with new tasks (and it
  blocked the quota for others).  Newly, there's a limit of at most
  eight consecutive builds or 30 minutes for one user (sandbox) on one
  builder and the builder is immediately terminated - which gives a chance
  to assign new builders to others' tasks (which have a higher priority at
  that point).