For timely protection, it is best to get vaccine doses within the recommended time interval. WHO recommends an interval of 8 to 12 weeks between the primary vaccination doses.
There is no maximum limit to receive the second or subsequent doses; it is never too late to get the missed dose if a delay cannot be avoided. The minimum recommended interval between doses should not be reduced because it is important to allow sufficient time for the immune system to mount a response.
Update (March 2023):
As a general principle, an interval of 4–6 months between completion of a primary series and administration of a first booster dose, and between booster doses. could be considered.