I Dont think theres any harm in a couple minutes lunging or in a round pen before getting on. In fact I like and prefer to do it to see what their mental and physical readiness is. From the ground an off step may be obvious lunging that wasnt yet while just being handled. Lunging/ rp lets the horse get some sass out if so inclined, before they are mounted and asked/ expected to 'straighten up & fly right'. I once put a Stoic school horse out in a round pen just to stretch, since Id never seen him out between lessons... He looked at me like "What? really?" when I unclipped the lead, and proceeded to Lose his Flipping Mind, bucking and running like a 3 yr old instead of a teenager. A passerby actually mistook him for a greenbroke trainee and not "old FC Gray". Numerous times Ive spotted a slight misstep lunging that curtailed or canceled plans to ride. Raps would do the 1st-2nd-3rd gear warmup on a lunge, and sometimes light the afterburner for a few laps, or til I told/ cued him to knock that off. Thats preferable in a pen or on a line vs that excess energy under saddle. BO has a horse that does not lunge, is clueless what shes being asked to do out on a line, and it always feels like a leap of faith to get on her cold without lunging a lil first.