Could the breathing exercises, performed during pulmonary function test, be done routinely?

Yes, no benifit : There is no benefit to do them to increase lung function. The best way is to build endurance is through a structured physical therapy program. Nothing can really increase lung capacity either. This is a matter of conditioning. You can do the exercise but no real gain. If you want to measure during exercise then a cardiopulmonary stress test is better. This is a dynamic test on a bike.