While Bitcoin halvings are conventionally expected every four years, the actual time between them can vary due to the protocol's self-adjusting mechanism. The 10-minute block time target ensures that approximately every 10 minutes, a new block is added to the blockchain.
However, as mining power in the network fluctuates, this target is met sooner or later. If miners collectively surpass the target, the difficulty adjusts upward, making the next halving occur later than the expected four-year timeframe.