In general, I feel that would be fine. The only reason that lapping normally starts at floor level is because it's usually expedient to rest the upper bars on the floor below. If you've got cause to lap someplace else, go nuts. The only caveat that I can think of is the usual one: high seismic design. Sometimes you don't want your laps to occur within the wall's flexural plastic hinge zone.
This is usually the biggest issue I think because you can get very long bars. Especially because this limits the use of factory produced reinforcement mesh.
It should still be fine I think if the seismic detailing area is increased by this lap length. I might be wrong on this one though.