Two house cats got to 15 and 16. Farm cats tend to get run over, or something else happens and they never return. But lost one last year who lived round the farm and she was in her early teens, so that was good.
Usually, its the old cats teeth that cause problems, and they tend to lose weight, although friend has a few toothless cats, and they are all ok!! And my two old house cats both had to be pts because of kidney failure - symptoms include drinking lots of water.