There is no correct number
How often you meet depends on schedules, friendship, attraction and what both people want. Internet rules about exact frequency often confuse correlation with a rule.
Watch for expectation drift
Frequency becomes important when one person interprets increased contact as growing commitment while the other sees it as convenience. If behavior changes substantially, talk about what the change means.
Do not use scarcity as manipulation
Intentionally withholding contact to make someone chase you may create anxiety rather than clarity. If you need more space, ask for more space.
A useful check-in
If either person is wondering “what are we doing now?”, that is a good moment to revisit the arrangement instead of counting days between meetups.
Use changes as conversation prompts
FWB advice often encourages people to decode every behavior: a longer text means attachment, a delayed reply means lost interest, a sleepover means the relationship is becoming serious. Real relationships are noisier than that. Look for sustained patterns, then use those patterns as reasons to ask rather than as proof of an answer. This keeps you from making major decisions based on a single message, busy week or affectionate evening.
Manage the agreement, not the other person
Boundaries work best when they describe your participation rather than trying to control someone else. You can say what information you need, what level of contact works for you, or what would make you step away. You cannot make a healthy casual relationship by turning uncertainty into surveillance or manipulation.
Labels help describe a relationship, but expectations are specific to the people in it. When something important changes, a direct conversation is usually more useful than trying to decode a rule from the internet.