Make sure they are in single level cages so they don't fall off of the second floor of their cage. Elderly animals may also need help cleaning themselves and may be incontinent. Check them each day for dried feces and urine and bath them if needed. I sometimes had to wash my Ares off because he has hind leg degeneration and cannot clean his private parts or belly.
Check their bed in case they have accidents on it, you may need to keep a supply of towels, fleece blankets or beds that you can easily wash and replace each day.
They may need extra help eating. My Ares started eating baby foods and softer human foods as he got older. The harder rat foods he wouldn't eat anymore. Sometimes you have to change their diets, their cages, bedding, beds, surroundings ect..just to make them more comfortable when they get older.
When my mom's dog got older she had to pick him up, take him out let him do his business and pick him back up and carry him back in her home. He wasn't into walking much when he got really old. As animals get older you have to care for them more, just as you would an elderly parent. You want to make sure they are as comfortable as possible.