SELECT
SUM(DurationSec) / 3.154e+7 TotalDurationYears # there are 3.154e+7 seconds in a year
from
(select
startTime,
endTime,
TIME_TO_SEC(TIMEDIFF(endtime, starttime)) DurationSec
from faf.game_stats
where TIMEDIFF(endtime, starttime) < '03:00:00' # ignore suspiciously big
and TIMEDIFF(endtime, starttime) > '00:08:00' # ignore suspiciously short
) qry;