Exercising with a personal trainer during 30-minute sessions may be enough to see results for people who have smaller goals and train three to four times a week. Typically, 60-minute sessions with a personal trainer will bring more value to most people in terms of meeting their conditioning goals. Lower cost and greater flexibility can produce a stronger experience for clients who can't afford more than one 60-minute session per week. In addition, a 30-minute approach produces multiple visits with a coach, providing the consistency needed to ensure lasting results.
Something your coach might suggest is something called “Supersets”, these aren't as scary as they seem (or can be depending on how brutal your coach is). Not everyone can afford to hire a personal trainer or fitness instructor for a full hour, and many people can't afford to have an hour off. The coach should know your goals and fitness needs and design a program during your sessions aimed at achieving those goals.