Just nitpicking, but I think a sortie was one trip on operations and thirty sorties, or trips, made up a tour of operations. If you were lucky enough to survive your first tour you were "rested" at an operational training unit. Accidents here were all to common and a lot of crews were probably just as happy to take their chances with the second "tour" from which very few would survive. Sixty trips were required before they could stand down and not fly on any more ops.
Statistics were such you could not finish the first tour. The cost of aircrew lost was a staggering 55,573.
Bomber Command survivors have been treated very badly by the politicians, and others since the end of the war.
There are a lot of good books on the subject for anyone interested, which will make you wonder at their incredible bravery and dedication to what turned out to be a largely thankless job.