I waited 5 years, but I'm a very patient person, and I wanted to feminize my face and body as much as possible before going full time. If someone is already retired, they have enough savings to comfortably pay for everything related to transition, and their significant other is accepting, etc., then nothing is holding them back, however, for those who rely on their job, don't have a lot of money, have a significant other who is unaccepting, then it may be more prudent not to rush into going full-time. And while you are waiting to go full-time do some work (e.g., practice voice, deportment, grow out your hair, get electrolysis/and or laser facial hair removal, present as your true self as much as possible, etc.) to ensure success.