Best practice for late stage diagnosis and if the person is well enough is to have Chemo and hormone treatment simultaneously. Chemo is relatively short duration and hormone therapy is normally for life (hence orchidectomy is an option instead of hormone therapy).
Life expectancy in PC is notiriously difficult to predict ( so don't try!). there are folks on here with late stage diagnosis who live for years and years (more than 10). Others sadly die within weeks of diagnosis.
Do what you are doing: keep informed and never give up!!