Steps to reproduce:

1. Create new LLD rule
2. Type name, key and set 1 in "Keep lost resources period"
3. Try save LLD

Result:
Get message "Incorrect value for field "lifetime": must be between "3600" and "788400000"."
But "Keep lost resources period" can also accept 0 value to delete entities immediately
Expected:
Something like "Incorrect value for field "lifetime": must be between "3600" and "788400000" or "0"."

This is actual for storage period too:
Item -> History/Trends storage period