Ninja'd!
In reality, the strategic bombing campaign over Europe seems to have worked because it whittled down the manufacturing and resource centres of the Axis. At the beginning of the day-time bombing campaign, losses were very often prohibitive, hence the big party when a crew/bomber made the 25 missions. Eventually, the Luftwaffe ran low on fuel, pilots and planes because of the damage inflicted on industry, and the 8th Air Force's losses decreased, making the strategic campaign's continuation viable.
The strategic campaign over Japan (not the south Pacific) was similar... the Japanese had a lot of home-industry, meaning people would go home and produce parts there too. So the US burned Japan down, by which I mean actual industries as well as residential areas. By then I think Japan didn't have the resources to produce much in terms of air defence, since they had lost most of their conquests which provided the resources needed by the industry. The B-29s flew high and were hard to intercept, but even if that were not the case it would've been a similar process to the strategic war over Europe.
But here we're talking about fairly small numbers of attacking B-17s, inhibiting massive concentrated defensive fire and long-distance attacks on forward bases, not manufacturing centres. So, presumably, losses in Japanese squadrons will be replaceable, since there's no effect on industrial capacity, whereas the attacking bombers will suffer significant fatigue, damage over target is likely to mean the loss of the bomber due to the long distances, etc etc. If it turns into a war of attrition, it will depend on the US's industrial and pilot training capacity... this early in the war, according to the figures Erkki just posted, I don't see it being sustainable. Especially for these marginal results of occasional runway hits on a lonely forward base...