Yes, it is a good practice to implement a limit. You should also do some research with relay operators to get an idea of the limit. Take a look at NIP-11. 

` {
  "limitation": {
    "max_message_length": 16384,
    "max_subscriptions": 20,
    "max_filters": 100,
    "max_limit": 5000,
    "max_subid_length": 100,
    "max_event_tags": 100,
    "max_content_length": 8196,
    "min_pow_difficulty": 30,
    "auth_required": true,
    "payment_required": true,
    "restricted_writes": true,
    "created_at_lower_limit": 31536000,
    "created_at_upper_limit": 3
  },
  ...
}
`

Check out:
https://github.com/nostr-protocol/nips/blob/master/11.md





I see, I'm planning to have a big structured data in a note but I should think about putting some hard limit for it.

NoStranger

nostr

What's the largest note you've ever seen?

In Long-form Content (NIP-23) there is no maximum limit, so the relays will set the limit.