Hi Roxanne! In answer to your questions it kind of depends on a number of things. You will need to consider your starting point, the level of your current hormones, what level of HRT you start out at (low dose or transition level), HRT delivery method, how your body reacts to HRT and any number of other variables. As many of the ladies here have pointed out, mid forties should not be an obstacle to transitioning.
Like many of the ladies here I began my transition later in life. In fact, I started earlier this year when I was 53. I am 54 now. You asked if FFS is needed to be passing again it depends on a number of factors. How comfortable you are with your appearance. Your hair and makeup skills. There can be a lot of variables.
To give you an idea of how fast the changes can occur, even for a later in life transition, here are some pictures.
(For reference I began HRT on March 2nd of this year. I went full time everywhere but work in April and full time everywhere on June 15th. I had FFS and BA on August 31st.)

This picture shows how I looked in March of this year when I started HRT vs how I looked last week.

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A couple of years ago and July 2015 (before FFS).

Eight years ago vs August (before FFS).

August 2014 and December 2015

December 16th (shows the results of HRT, FFS and breast augmentation)

December 2nd Post FFS and BA
I was full time I believe I was passing ok relatively quickly. Once I got my hair colored and styled and I got my makeup skills learned I was very confident in my appearance. The other things that you will need to work on besides your physical appearance is your voice, mannerisms and walking skills. All of those things affect how you are perceived by others. Believe it or not I still get the occasional "sir" comment when someone isn't paying attention because of my size. I can be in a skirt with red lipstick and nails, large hoop earrings, full Smokey Eyes with a plunging neckline blouse showing my 38C boobs and get "sir'd". I laugh when that happens.
Good luck and get ready for the ride of your life.