There's not really a specific best practice for NAS checkpoints NFS and CIFS file systems because there are different business usages and different business requirements. It's best for you to determine what your business needs are. What is your recovery point objective -- at what point do you need to recover back to if there is a problem? And, how long is that recovery point available? You really need to establish what you do, based on your own business requirements.
What you're doing now may be what you need -- it doesn't seem excessive on the surface.
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How to compare NFS and CIFS for Red Hat Enterprise 4?
Read an expert discussion of NFS vs. CFIS