Write cron business logic as a Python class and let this app do the rest! It enables Django projects to schedule cron tasks, tracks their success / failures, manages contention (via a cache) etc. Basically takes care of all the boring work for you :-)
If the big job lasts more than 1 minute, there will be multiple executions of the same job (one every minute until the job is finished).
That's because the log of the cronjob is only saved when the job is finished.