Those 300 hour cadets are going to learn precious little in the next ten years if they stay on the 744. If they do 10 actual sectors (T/O and Lndg) per annum they will be considered lucky. 5000 hours and 50 landings in 5-7 years (working hard) won't qualify them for much, certainly not a 744 command and probably not even a 737 command. I doubt very much that they will be fully qualified as F/Os for quite some time.
You need to work up to the jumbo, earn a right of passage. They may be cock of the walk now but will be rueing the day (IMHO) they went straight onto the heavy metal.
S