Don't worry - as long as they are normally cared for and on a normal general diet, you give them every chance of having a good and long life, provided there is no unexpected illness or hiccup.
Tegan, the little surprise baby in my avatar on the left, joined the big Tribe group at 4 weeks old together with her mum and shared their normal adult diet. She died in summer 2019 at nearly 8 years of age together with her smaller childhood playmates I adopted as her company and who came from one of the worse backgrounds and Tegan's auntie Ffwlbri - they all passed away within 3 months of each other at 8 years of age. Tegan and her friends were never majorly ill.
It is the hay/grass based diet with only a modicum of pellets that wins the long term race any day. keep in mind that the actual extra amounts are truly minute when you come to guinea pigs. It is more the customer demand to have baby specials for every species than the actual need.