Disclaimer: the following figures are just a rough estimate.
If you fly long-haul (like I do) you spend most of your flight time in cruse, and as a rough figure we have a ground speed of about 480 knots (nautical miles per hour) at Mach .80 with no wind. Since a pilot spends some of the 'flight' time on the ground, and flying slowly on approach and landing, I'd guess the overall average speed for a longhaul pilot is maybe 450 knots. And for a pilot that makes more landings per day it would be less, maybe an average of 400 knots or less.
By regulation (US) pilots can fly a maximum of 1000 hours per year which would give a yearly maximum distance flown of 450,000nm for longhaul, and 400,000nm (or less) for shorthaul pilots. However most pilots don't max out their hours because of contractual limitations, vacation, training etc. A more realistic figure is 70 to 80 hours per month, or 370,000 to 432,000 nautical miles per year in flight.
There really isn't much difference between a 757 and 744 pilot, because their cruise speeds are close to the same, and they are limited to the same number of flight hours per year. The 744 pilot just gets his hours (and miles) in bigger chunks, with more days off between flights.
Hope this helps.
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.