Bit surprised at that. I've recently done some work for a UK firm who, "in theory", took over a big US company who are big hitters in the downstream oil business and, I think, DD took about 4 months
I say "in theory" because although it was theoretically a takeover of a US company by a Brit company in reality it was more of a merger and due diligence was carried out on both sides. Can't argue with what you're saying that, each case is different and it may well be that, paradoxically, because quoted companies are subject to stricter controls that DD is somewhat simpler than it is for private companies.
Anyway, I'm wittering. Time will tell on this and we'll know sooner or later.