Approval/hold jobs have a 90-day limit on when they can be approved.
While after 90 days they can't be approved, workflows will remain on hold until canceled, we don't automatically transition an on-hold workflow out of its current state.
Jobs that use Workspaces
The only caveat to the above is jobs that utilize workspaces.
If the job after the hold job utilizes a persisted workspace, there is a 15-day limit before the workspace expires.
So while the approval job can still be approved for up to 90 days, the workspace will not be available and the subsequent jobs will fail.