I would have no issues doing this to short haul. To a long-haul, what are your options?

Norwegian via Gatwick (or non-stop to JFK) is quite reasonably priced though, at least far enough in advance, for a one-way.

Equally, you could have miles availability, especially if you get enhanced options as an Exec Plat. All that said, I'd either do an overnight in OSL or (probably cheaper) get the late OSL-LHR and then an overnight in LHR before flying on to BOS. Under 24 hours will still not be a stopover.