A Single Man

I watched A Single Man yesterday. Maybe my expectations were too high, but I was somewhat disappointed by the movie. The story is about George (Colin Firth), a middle-aged University professor in the early 1960's who has lost his (male) partner after a 16-year relationship. From the beginning of the movie, we see him making preparations for the suicide he is planning. He has one good (female) friend Charley (Julianne Moore), who has been left by her husband and still regrets that she and George are not together. A young student Kenny (Nicholas Hoult) tries to get closer to George and in the end they get drunk (and naked) together.
On the one hand, the movie didn't bore me and I liked the tension that develops in the relationship between George and Kenny. However, it doesn't become clear from the movie why George wants to commit suicide (we know he lost his partner but as viewers we don't feel the loneliness and sadness that George apparently experiences). Also, two beautiful young men basically throw themselves at George and he doesn't accept the offers?
This movie should have been longer - the characters could have been developed better.