Seems I have arm veins that are easy to put needles in correctly and /or a good run regarding ability of those doing it. In just on 100 blood donations have had one miss - a female doctor put needle through a vein. Her embarrassment was more significant than any problem though. Was simply tender for a bit longer than the other arm she was successful with. Only one other near miss from one who by her manner appeared to be a learner at the job. A small bruise from apparently *****ing the vein inside.
I gather normal practice at hospitals is that with people who need to have needles regularly put into their arms, especially those whose life depends on it, only proven competent people touch them. It is important not to damage the easiest veins to insert needles into.
Regarding visiting blood banks, my normal practice has been to fit it in when near one for other reasons and usually drop in unannounced. Have found it rare that they are too busy to accept an extra donation, even if means waiting or coming back a bit later.

