6 years is about average for indoor pigs.,although they can go to 9 and beyond.
I treat my oldies the same as my other piggies,although they do get more thorough health checks every day.I treat problems if and when they occur.
All my pigs are on vet beds anyway,so the oldies are warm and dry.I do keep an eye on urinary input/output.
If I have a pig that is starting to look frail,I give one drop of Abidec about 3 times a week and hand feed veggies twice a day to make sure they are getting their share.Frail pigs will sometimes let other pigs take their food.Having said that,I have an old lady who is very tiny and frail,but woe any pig that tries to take her food!.She is amazing.I have been expecting her to collapse every day for the past 4 months!.