My mom and dad both have pacemakers. one goes into the office once/year to have their pacemaker checked, the other goes in every 3 months. why?

Pacemakers: Probably different models of pacemaker; as technology improves, the size & quality of pacemakers improve. Some can be monitored over the telephone. Other variable may be a different degree of cardiac illness in your parents, so that one must be monitored more frequently.

Pacemaker: Likely one is a pacemaker/defibrillator and one is a pacemaker. The pacer/defib needs to be checked more frequently and can be done in the office or over the internet. A pacemaker can be checked once or twice a year in the office and then once or twice over the phone. As either device gets older then it will need to be checked more frequently.