To keep your Jobs list looking fresh and relevant you'll need to archive jobs once they're completed and invoiced.
A job is considered Complete when all Items have the Complete status. See here for info on Item Stages.
You can archive from the Jobs list or the job card. Just click the hamburger to the right of the job and choose to archive the job.
Should you need to work on that job again, restoring a job is easy - just follow the same actions.