No IV antibiotics with my 3-month kidney infection last year - but it was 'third time lucky' when it came to the right antibiotic. My bug was resistant to the first two they tried, which is how I ended up so poorly as it was therefore not being treated, as such - thankfully after that 2 x 7-day courses of nitrofurantoin did the trick for a bit, with a further 7-day course about a month later when it came back.
The drip, although sounding dramatic, might just be the thing that finally gets rid of the bug - if it were me, and if that is what they're recommending as the next course of action, I'd bite their arm off....!
Great news re the kidney stones (lack of, that is!).
Hugs!