Thank you all for your help. I will share a few answers I received, but have not been posted here:
A new NetApp article from last week on how to set timeouts for the different guest os I have:
https://now.netapp.com/Knowledgebase/solutionarea.asp?id=kb37986
Also some tuning of the following parameters on the esx servers can be done:
o NFS.HeartbeatFrequency o NFS.HeartbeatTimeout o NFS.HeartbeatMaxFailures
I have been told that with the default settings the timeout seems to be 30 seconds.