@alicebrew1 HI, I'm not sure what especially concerns you, and what condition you have that Trelegy is meant to treat.
Most combination inhalers are prescribed to people with progressive lung diseases like COPD, or chronic conditions like asthma that have not responded to more conservative measures. They are generally meant to be used long-term, and your doctor should consider possible interference with other medications and your other health conditions before prescribing it.

There is an increased risk of pneumonia (about 2-3%) for some people, but there is also a decreased risk of other exacerbations - so a balancing act.
People who have heart or kidney disease, osteoporosis, diabetes or hypertension or are on antibiotic therapy need to work with their doctor to determine if the benefit of better lung function outweighs the risks of long-term inhaled corticosteroids, and probably need extra monitoring. This will very from person to person.