He's not the type to stay out overnight. But if your mare is happy out and well rugged, why not. I have found he us much better out than in.
With regards to exercise, if I have a long ride planned I will gradually increase his over a few weeks and the afterwards scale him down slowly back to...
We have a gelding who we have owned for 15 years. He had his first attack of tying up when he was about 6 yrs and the vet said that it was due to a complication of a virus he had at the time (unknown to us).
He then had a few more bouts of tying up but with careful managment has not had...