As has been mentioned it can vary...
For example whilst the 3 in 90 days is in our manuals we are further constrained by the
commander needing to do a take-off and landing at least once every 35 days and co-pilots need to have been at the controls for a takeoff and landing at least once every 35 days.
There is no minimum monthly hours requirement and the simulator can be used to retain recency, or regain it.....
Whilst fundamentally recency is an individual responsibility at our place it’s also tracked electronically (haven’t seen either a chinagraph or Perspex stats board in years). The landing pilot’s name code should
be transmitted back to base via ACARS after engine shutdown...the “system” flags up any potential recency breaches to the Ops folks a few days ahead of expiry - they then chase the individual, usually initially by e-mail.