If a shop-built wheel is shot in 50 miles, they don't know what they're doing. Find somebody else, or learn how to do it yourself. For the latter, get a copy of Jobst Brandt's book, "The Bicycle Wheel," read it until you understand it. Finding somebody else is a crap shoot. There are a lot of mechanics who claim to know how to build wheels, and some 125 pound cyclists will recommend them because they're wizards at getting a bend wheel back into shape, but they don't know what they're doing as far as building wheels for heavy riders who ride a lot.
The two biggest parts of a long-lived wheel, IME, are adequate spoke tension and stress-relieving the spokes. I've hovered around your weight for years, and stress relieving my spokes cut my failure rate by about a third; buying and learning how to use a tensiometer made an even bigger effect on reliability. I've gone from having broken spokes laying about for everything from clearing mud out of my shoes or fishing a chain out of wax, to "I thought I had a spoke, where is it?" Perhaps a tertiary factor is correcting the spokes' line while building; if someone worries about that they are either ace builders or, if they don't obsess about the first two, maybe they'll learn eventually.