How much sex and how unknown do the strangers need to be? s4 had Jamie and Anna, but s3 seems to have been the last time he went on a roll of just picking up random people.

They did seem to be intending to show some revival of casual interest in scoping out women in the latter half of s6 (6.13, 6.18), but I think he had basically moved on to a more monogamous phase.