apply as early as possible 🙂 it's easier that way! because the schools have rolling admissions, it gets more competitive as it gets closer to the deadline.
most schools start accepting applications in august/september, so check the websites of each school you wish to apply to, to find out when they start accepting. you can also have the school send you a hard copy of an application so that you can start working on it/see what it looks like, but applying through the web was easier for me 🙂
as far as LOR, it's always good to have more, than less. the key is to have the REQUIRED letters (optometrist, professors, etc.) so be sure to check what the school requires, as they vary among schools. Also, some schools will tell you that they will only look at the required letters, and if you submit any more, they will not bother to look at them. it's different for each school, so just speak to an admissions officer and they'll let you know!
Good Luck!