I had my mastectomy six years ago ( nothing prior - hoping nothing after too!). No reconstruction - never fancied it, didn't feel I wanted it (68 at time of surgery too - not over giving someone else a thrill, but definitely over breast feeding!). I haven't changed my mind, and I haven't decided to have a second mastectomy. I have discussed it with my oncologist (the second mastectomy that is - my surgeon will happily do a reconstruction any time I want, but hasn't taken the lack of interest personally).
Oncologist knows of nothing that would suggest a second mastectomy as a useful procedure. I have no (known) tricky gene, and no family history of cancer (breast or otherwise). I am more likely to get a new cancer somewhere else in my body. After 6 years my chances of a recurrence are shrinking (but not gone). I developed a persistent and very large seroma (not a given for a mastectomy of course but my body went into a bt of overdrive and, more important, may do it again for a second mastectomy). So I finally got my prosthesis almost a year after surgery. Took about a week of adjustment ( nothing painful just a slight ache) as of course I had been walking lopsided for 12 months ( large boobs). Beyond that, I have experienced no difficulty.
I am on my 2nd prosthesis (last about 2/3 years or so), it's silicone and while some women find them hot, I don't (I live in Melbourne). I had it fitted at home -the weight is right - 12 months with a soft pad can drive you slightly mad as it rises every time you bend and is to be avoided! I don't swim much but do, and just slip it in my swimsuit- worth getting a special swim prosthesis if you swim a lot. I wear the same sort of clothes I wore before - was never one for plunging necklines. My surgeon left me a tiny cleavage!
Do I worry about the other breast? Occasionally, pre scan anxiety although that got MUCH better after five years. I don't regret leaving my other breast there. I am fine with the way I look, don't strip off everything in public much but have done so ( Icelandic hot tub!) and guess what? No-one batted an eyelid.
I thought at first I would never get the hang of "just slipping" the prosthesis into the right place in my bra - it landed on the floor, looked like a Monty Python skit! But of course you do, quite fast. I occasionally worry I will head out without it one morning, as it's now not a conscious action but I haven't so far. I had to finally have surgery on the old site to fix the seroma (BIG infection) and that feels like enough surgery for me. Good luck whatever you do.