The details of the Presidency were described by the second charter, and initially did not have any limit of how long a president could serve; by current society statute, he cannot serve for more than 5 years.
The details of the presidency were described by the second Royal Charter, which did not give any limit for how long a president could serve and there were considerable fluctuations of of a president's term of office until well into the nineteenth century. By current society statute, a president cannot serve for more than 5 years.