usually air-con life cycle is 5 years.

Anyway, the air-con still "powerful blow air" or not when you set the max fan speed?

Most likely pipe sumbat, the fella didn't do a good job.

If air-con still cold do a thorough cleaning to clear the blockage or change the pipe. If you set the fan to max, and still like "blow air" not powerful, time to change. If not cold, can be due to time to replace gas.

Best get a trusted aircon technician to check.