if someone else is at the yard and can see your horses and would notice if something was wrong (and do something about it!) then i think you are fine with going up once a day. How far away is your yard from home and what kind of ours do you work, would it not be possible to fit in a quick 10 mins visit to check, break ice and throw in some hay either in the morning or evening depending on when you have the most time.
I must admit though as a teen with my own pony i would visit twice a day both in summer when they live out (which was literally just a check in the morning and i'm sure i was the only one who went up) and in winter when in overnight and sometimes i do wonder how i managed to do the early mornings, back home from the yard at 7pm then having to get all my homework done and still managed to get good grades in my gcse's and a levels...lol and how people manage when they work full time i will never know, hats off to you all