According to some opinions, Pharoah was the same from when Yosef went to Mitzrayim until Krias Yam Suf, and he was the king in Ninveh when Yonah went to warm them of their immoral behavior (Yalkut Shimoni Exodus 176). According to them, how old was Pharoah when we last hear of him?
The year that Yosef was taken out of jail and brought before Pharoah was 2229 from creation (Seder Hadoros there). Pharoah was king for at least two years prior. I could not find the exact year that Yonah went to Ninveh, but according to Seder Hadoros was somewhere around 3055. This means Pharoah lived for at least 800 years.