My fiancé and I were talking about starting a "baby chest"

Car seats, cribs, and other big "gear" items expire after 5 years due to safety regulations. You can't be sure of what size your baby will be or how quickly they will grow so be careful when buying diapers. Sometimes it's necessary to try different brands of diapers if your baby is sensitive to certain brand or if a brand isn't absorbent enough. Other products like shampoos, diaper creams, etc. can cause allergies and don't hold up well to long term storage.

I would suggest simply putting the money you would spend on baby products into a savings account. That way you'll have some money saved to help with expenses and you'll have the freedom to try different products. And when you do get around to buying things it's best to go with natural and organic products. They don't have harsh chemicals and aren't as likely to cause allergies or irritations to your baby's skin.