@kaili -I dont knwo about other university , but UT@ Arlington denied to sign my travel I-20 before my class started. I had to wait till the middle of the semester and Finally they signed it . I didnot had any associate but ofcourse I was transferred there from another college.
@Birkrishna- UTA used to issue us temporary I-20 at first which clearly mentioned that it was temporary . So that would not count as travel I-20. They used to take 2 weeks to issue us I-20 with advisor's signature ( that would be new i-20)

I know a guy who continued his master ( without taking opt) and went back to nepal for a month during the break without any problem. He joined master at same university if that matters.

I feel like it depends on university strategy. Abi, you may wanna see your Intl advisor or save it to next sem just to be in safe site.