Same Problem... disable perfbeat is not supported, but you can change it to 60mins.
Answer from support:
The developers have come back to me regarding disabling perfbeats. We are not allowed to give out unsupported configurations. If you were to do this then you would have to this yourself. To change the perfbeat timeouts it can be set to a maximum of 1 hour. By default it is set to 5 minutes (300 secs.)
The command to change the value to an hour is
#avmaint config perfinterval=3600 --ava
From a support point of view there anything further you need at present? It has been a pleasure dealing with you on this case and if it is ok with you we can achieve the case for now and reopen or reference it in the future should the need arise.
regards
Reto