I know it's a taboo subject here and hardly qualifies as "running" but humor me.
Is it really necessary to have the ever so popular back to back weekend long runs that most ultra marathoners seem to incorporate? I've not seen many "elite" ultra marathoner training logs but the hobby jogger turned ultra runner late in life seems to swear these are an absolute necessity. Just doesn't seem right to cram 40-75% of your weekly mileage into a Saturday-Sunday double. IMO, one would be better off accumulating mileage through the week and hitting one solid long weekend run, like typical marathon training.
Example Peak Week - which is more ideal for training for a 50 mile Ultra
A. M-5 T-15 W-10 T-20 F-10 S-10 S-30 Total 100 (midweek long, weekend long)
B. M-5 T-10 W-12 T-12 F-10 S-20 S-30 Total 99 (typical ultra training)