Keeping it simple is the key.Too many options leads to confusion, mis-understanding and lots of complaints. Besides, no HR person is going to learn the differences in so many services or be inclined to spend time explaining them to everyone who asks, and they will ask!We offer 15 or 30 mins. We used to offer anything from 10 - 30 in 5 min. increments but it became a nightmare calculating the cost, paying for 5 mins of down time and filling the schedule.the only rule I would impose is employees paying ala carte should never pay less than the company would for a block of time, which pretty much prevents you from charging the dreaded $1/min.