This question was recently posed by a photographer to other photographers. The majority of photographers think that age does not matter however; some believed that it does and others believe that it depends on the genre of photography.
Those involved in architecture thinks that this type of photography is better served by photographers with more experience as it takes time to know where the shots are and following through with corporate clients becomes easier with experience. Whereas some believe that 25-35 year old photographers will relate better to high school seniors.
One photographer said that he was sent a prospective client by a former client who wanted to get some shots done for a modeling portfolio. He met with her and they spoke for about 30 minutes. At the end, she told him she did not think they were a good match because it was "just too creepy" posing for someone old enough to be her father. This exchange had another photographer wondering if these aspiring models think that all fashion photographers are in their 20s and 30s. He continued to say that yes, most of the models are very young but many of the top designers, photographers, editors and other creatives have been around for years and that it takes time to build a career and reputation.
My philosophy is that sadly, age does matter to some clients and this is not exclusive to photography. If a photographer's portfolio attracts someone, then that should be the main criteria for hiring that photographer.