The best time of the year for travel agencies is here, with most of their overseas tours for summer vacation sold out.

"More than 70 percent of the tours to Russia have been sold, and tour groups to Europe are more popular," said Wang Zhenyue, deputy director of the direct-marketing center at the UTour International Travel Service Co Ltd.

Posing in front of the Sydney Opera House. As Chinese travelers gain more experience with overseas trips, "depth tours" to a single destination are popular this summer for the first time, business insiders said. [Photo / Agencies]

The agency, which is a leader in outbound travel service, has offered hundreds of tours this year, with some departing as early as May.

Once the vacation season actually starts, it's too late for agencies to plan a tour and too late for most customers to book one.

"Maybe I should postpone my vacation to September," said Li Jing, 28, who is planning to take her annual leave with her boyfriend.

Li said they originally intended to join a tour in early August that covers some European countries, including France, Italy and Switzerland, but they only can get places in a tour leaving in late August.

Li said she is thinking it might be a good idea to postpone their vacation to September. By then, the peak season will be over and prices will be lower.