The rule is simple: FAIRTIQ must be active when travelling, and stopped when not travelling.
FAIRTIQ sells and updates tickets as you travel
The frequency of starting and stopping your trips throughout the day won't impact the final price. In fact, the system may even combine several trips if the overall cost is lower than the sum of the individual trip prices.
In specific German regions applying the beeline fare, starting and stopping a trip might result in a new base fare.
Short connections/transfer
Keep FAIRTIQ activated when you transfer between public transport services, e.g., switching between train and bus. If the transfer takes longer than 25-30 minutes, end the trip.