I often workout twice/day I run in the afternoon and hit the gym at night... Sometimes I workout 3 times /day, like today, I will run once with a client (50 mins.), have an hour break, then again with a friend (40 mins) then tonight hit the gym (35 mins)... It doesn't happen often but it's doable once or twice/month...I sure am exhausted when I hit the sack

sleep like a baby

... One thing I do notice is that it kick starts my weightloss quite a bit...
Your body will tell you if it's too much, you'll be overly exhausted for a long period of time or injuries will occur...
So, I guess I'm saying no it's not too much to workout twice a day if your body says it's okay...