IMO: What is a good frequent executed cronjob entry?

I think …

33 3 * * * svn up -q ~/svnroot-data; ~/svnroot-data/cronjob.sh || echo "E: exit-code=$?"

1. Daily execution
2. Automatic silent/quiet update; always be on the edge
3. Run your script
4. Print the exit code if it’s not zero

You will get a mail only, if there is an output or the exit code says error.