Turbantime,
From what I understand, there is no extra flight-crew requirement regarding flying the A330 and the A340 on seperate days. As long as the crew is qualified on both (i.e CCQ), then the airline believes that they are compotent enough to recognise the differences in such things as TOW, Rotation Speeds, RoC and general flying techniques etc.
There was rumour that this was one of the factors (CCQ) involved in the EK A340 incident at Johannesburg earlier this year.
Soulman.