Question
What is the average life expectancy of a Saguaro, once it has been transplanted?

Answer
Greg,

Probably the same as a non transplanted one (with one exception, overwatering). There is no real way to determine the age of a saguaro, but it has been estimated that the largest ones you see around the desert may be up to 300 to 350 years old. Hope this helps.

Sincerely,

Greg