When 86400 is not a multiple of timekeeper.epochLength(), runwayDays might be longer than it should be.
Let us assume that timekeeper.epochLength() = 43201 (about half a day), and runwayEpochs = 360 (about 180 days).
runwayDays should be runwayEpochs * timekeeper.epochLength() / 86400 = 180, but in the above implementation, epochsPerDay = 1 and runwayDays = 360. 
It is recommended to use runwayDays = runwayEpochs * timekeeper.epochLength() / 86400 directly without the middle variable epochsPerDay.
