Like minty I had a mastectomy and immediate DIEP flap reconstruction, though not preventative. I was very lucky to have a great plastic surgeon and BC team looking after me (not at the RM but by all accounts RM is a centre of excellence for BC) and I could not be happier with the results.
I was apprehensive having never had surgery before. The DIEP meant a longer recovery time, and the large abdominal incision meant I had to be bent over walking and uncomfortable lying down as I couldn't lie flat. While I was mobile within a week and able to sit and walk upright in two weeks, it took 5 to 6 weeks to really start feeling normal again. Before then, I had to take it easy: no housework, cooking, lifting things, driving, etc.
I chose DIEP as I wanted to use my own tissue. Implants need replacement, albeit after years; but as minty said, there may need to be further adjustments, so it's not like you will be absolutely be done with one surgery for DIEP, or for most other options for that matter.
The other 'own tissue' option I considered was using fat & muscle from my back (an LD flap), but I felt taking the fat and skin from my spare tyre and using it to construct a new breast was an elegant solution. For me, it was well worth it for the 'tummy tuck' effect. It's not the same procedure as a tummy tuck; my scar is not as discreet, but fat gets taken from the belly area, which is a win in my book.
The fat feels and behaves like normal breast tissue, and I don't have to worry too much about over-excited children bumping into it. I'm also a front sleeper, so again the fat is more robust than an implant in that regard.
Surgery is very much individualised so do talk to the surgeon to ask about preserving the skin and nipple, and what they recommend. OP and Isadora, hope you find an option that works!