Went to the Dolomites for the first time last year and did no specific training beyond lots of climbing (but then my friend and I don't climb that hard and didn't do anything beyond V+/VI-).
None of the walk-ins were that tiresome, but I guess that depends on where you go. The longest we did was walking up to the Vazzoler Refugio, but as it was fucking pissing it down and we weren't climbing & were in no rush (took a bit over an hour). Oh yes, we walked up to Cinque Torre rather than taking the chair-lift, that took about an hour too, but was pretty easy going.
Can't see that generally being fit for long days would do you any harm though. Cycling to the wall is always a good idea in my opinion as it raises your heart rate & body temperature gets the muscles warm & working. We shared a rucksack with the second wearing it (or trailing on chimneys) although are you perhaps adding weight to simulate rack?
Only had one party climb through us mid-route, but then the forecast for the two weeks we were there wasn't brilliant which I suspect was keeping many off of routes, didn't actually impede our climbing though really as we were just adaptable (i.e. climbed in rain, mist, snow, hail and occasionally sunshine). The guy leading had been quite keen to start following me up whilst I was on the crux of the six-pitch route though!
Most of the routes we climbed didn't have many bolts to be loose, predominatly pegs of varying age were in place. Only had to be wary of loose rocks from above on one route but again that was likely lucky and down to the poor forecast keep people away as the party above were Russians (of the three only one appeared to be climbing the other two were jugging up which seemed retarded given it was the third Sella Tower and not very steep, just looked harder work than climbing to us with the disadvantage that you knocked rocks on those below you).
