Generally I only restart my ZCS when it needs it. (occasionally java goes wonky for me) Or, of course for upgrades.
The redolog is an internal function, more like a double-check on what the server has done. Mine seems to peak at about 100-120 megs and cycle onto a new file, and it keeps a few in logrotation.
I don't know that they're used in the OSS version, but I could be wrong. Here's a good explanation:
Question about redo logs and disaster recovery