To exercise once a day or split it up

It depends

It depends entirely on your schedule and the type of exercise you're doing, how long you've been working out etc.

My inclination would be to suggest that by the later stages of a 2 hrs session you may be sufficiently fatigued that you're not employing proper form or working at the right intensity unless you're already quite fit.

It depends on the workout, intensity of what you're doing, goals, etc. For me, I split everything up. On lifting days, I lift and I go hard...when I'm done, I'm spent...no way I'm doing anything else. If I do something before I lift then I bonk on my lifts. At most I take a long walk at lunch on lifting days and lift in the evening. On non lifting days, I go balls to the wall with my 10K training, including tabata warmups. That pretty much does me for the day. I take Sunday off and perform recreational "exercise" only...like walking the dog, taking a dip in the pool, bike ride with the kiddos, etc.