If loaded on a clean barrel, it don't think it won't hurt it. I often load mine at the start of the season and unless I shoot a deer with it, it stays loaded for several months with no issues. (on clean barrel only)
I can't say for 100% sure on Triple 7, because I use pyrodex. But I left one of my guns loaded one year (by accident) all the way until the following season and I had no issues. In fact, when I finally shot the gun the following season I killed a deer with that load and it fired perfectly.
That said, I wouldn't knowingly leave it like that though for the whole year, you should go ahead and unload and clean it. Always better safe than sorry. If you can't shoot it out, push it out.