Men's tuxedo fashion does change as does men's weight. They will not like to buy or rent something so far out from deadline just because you don't trust them to do it themselves. Have your partner reach out and assist their own people.
I don’t necessarily think the guys have to place the order early, but you might have your groom start looking at inspiration/coming up with ideas if he’s indecisive or struggles with that kind of stuff. FH and I started his search last month, and he was so lost when we walked into Jos A Bank that he just stood staring blankly in the middle of the store for several minutes. 😂
Presumably the groomsmen are mature adults who are capable of placing an order without prizes or an artificial date seven months in advance. I don't think it's necessary or appropriate to imply that they aren't.