Having worked horrible shifts as a junior doctor - Friday 9 am to Monday 5 pm for example - now thankfully illegal - I think you learn what degree of sleep deprivation you can - and cannot - cope with, but I don't think you can train yourself to cope with more. You just become intimately aware of your limits. Some can clearly cope far better than others.
You are so right about the weather - it was absolutely perfect here for several weeks - if only .....