This study investigates the operation of multi-stage air-source heat pumps (AHSPs) in non-retrofitted multifamily buildings (MFBs) with high ratios of space heating (SH) to domestic hot water (DHW) demand and limited storage. Hourly monitoring over one year in an eight-story building in Geneva reveals that compressor activation delay significantly influences cycle duration and frequency. Complementary dynamic simulations evaluate step-by-step activation of dedicated SH and DHW HP units, under varying outdoor temperatures, storage volumes, and HP sizing. Results show that adjustable activation delays are essential to balance cycle duration, thermal comfort, and equipment longevity, particularly during cold periods. Sensitivity analysis highlights the importance of storage volume for mitigating short cycling and maintaining SH/DHW temperature setpoints, whereas oversizing HPs alone is insufficient. Findings provide guidance for cascading strategies in large MFBs and emphasize the need for integrated HP control to optimize efficiency, comfort, and system reliability.