In most cases no. The ductwork is already sized for the heat pump itself. So a larger heat pump would need larger ductwork. The problem may be due to undersized ductwork, poor system design or installation. You may need ductwork modifications, a heat load calculation, or possibly an energy audit to find the problem areas and correct them.
Some people are just never happy with a heat pump even if it is working perfectly fine.
They just can not get used to the lower temperature output as compared to an oil system for example. It can vary, depending on how much the system is used and how regularly it is checked or serviced. Generally, the average life-span of units built in the 1970s and 1980s is about 15 years, but individual units may vary and last much longer depending on use and how well they are maintained. An ARI survey showed average heat pump life to be about 14 years when recommended maintenance procedures were followed. Newer units are expected to last even longer.