More info needed. If someone is on the ventilator, the time it takes to get them off of it is highly variable and individual. The reason they ended on the ventilator is a big part of the answer, together with their age, the severity of the illness, what other things are going on ...Etc.
Depends. Depends on how bad the COPD is and what the patient's wishes are. If the COPD is really bad, some patients may need to be on the vent for life unless they opt out of it. If there is something reversible such as a pneumonia or congestive heart failure exacerbation, would be reasonable to wait until that is treated before making decisions.