Martin Boehm and William Otterbein were elected bishops in 1800, when the denomination officially organized. The understanding was that these were four-year terms, which meant they would hold a new election in 1804.
However, only five people showed up for the 1804 meeting. There was some kind of epidemic going on, probably yellow fever or cholera. Boehm was there, but not Otterbein. So the election was put off until 1805. Thus, Boehm and Otterbein started out serving five-year terms.
The 1805 conference began on May 29, 1805. Both Boehm, 80, and Otterbein, 79, were among the 21 ministers who attended, and they were re-elected as bishops.
That was the last conference Otterbein attended, though he continued as bishop until 1813. Boehm attended most years up through 1811, presiding alone. When neither bishop attended, Christian Newcomer and George Geeting presided.
There doesn’t seem to be any record of Boehm and Otterbein being re-elected in 1809. Nevertheless, we have traditionally held that Boehm and Otterbein served as bishops until their deaths in 1812 and 1813 respectively (both at age 87).