730 was a number.
When he met Sharon Davies, the Doctor claimed to be 730 years old, and blamed his age for his faulty memory. (COMIC: Doctor Who and the Star Beast) Another time while travelling with Sharon, after ageing four years due to the chrono-compensator, he decided he would still think himself as "743... or was it 730, I never can remember". (COMIC: Doctor Who and the Time Witch)