I took 40 minutes creeping 250 yards into a part of the wood where they were visible on thermal, but always 60-100 yards away, when I eventually got to the edge of the wood, they decided it was too warm to be out, so retreated, unhurriedly, to dreys.
40 minutes! not a shot on, cue old bloke in wood muttering to himself.
Still, I went back today and ended three of those buggers.