There are differing opinions. I have heard vets say 6 weeks for any whole food animal in the freezer. But then again, reptiles have a different digestive system than dogs and cats. On the flip side, hobbiests have fed rodents to snakes where the rodents have been in the freezer for a year (w/o the snakes dying).
Vaccuum sealed may go 6 months and still be OK. OK means that the snake will get some value out of it. For non-vaccuum sealed, I try to stay under 3 months, with 2 months being the more optimum goal. I base this OPINION on the stool consistency of the snakes when fed frozen food. If the stool looks normal, then the food must be OK. I could be wrong, but it is a safe guideline IMO. No problems yet going by this.
For you now, you may add a little vitamin supplement made for reptiles on the 7-month-old frozen pinks (maybe every 3rd feeding), or else supplement some feedings with fresh food.
Eating more non-nutritious food is like eating more twinkies - you get calories but nothing else.