I voted for twice a session. Much less than before, since I have Proflex, as the lacing only goes so far up the boot, then there is a knob to turn to tighten the upper wires.
For Synchro, I usually do the laces up, tighten upper wires, re-tighten laces & adjust wires.
For Figure skating, as above, then adjust wires only once during session, after warm-up, unless I'm doing a lot of jumping. Once I start to jump above salchows, I need to adjust the tightening again.