Might be completely wrong, I am sure someone will correct me. But I've hooked into missing as event when I need frequent updates on a custom tag. (Also I think .frequentUpdates is only for statusbars)
Like so :
Lua Code:
oUF.Tags.Events['mu:petname'] = oUF.Tags.Events.missingpp
Admittedly, it's also for power - but in your case I think it may work fine.