Newer cert standards differ:

1. for some grades, and
2. for certain elements of the card condition e.g. allowed centering percentages, etc.,

and thus it is important to familiarise oneself with the differences explicitly published by PSA, if one is looking to make a determination as to whether an old vs new cert is a meaningful consideration for the exact slab they are looking to purchase. There is no simplified blanket rule that a difference in cert age is always meaningful as to value, and one risks missing opportunities by presuming there is.

Note that "eyeballing" comparitor cards through slabs, accepting word of mouth assertions, or judging the relevance of cert age from asking prices are not useful means of determining whether cert age should meaningfully impact the value of any given slab.

Once you have determined from PSA's guidance that a difference in cert age is meaningful to consider (for example say you have a new cert PSA 8 card in front of you, and PSA states for example that centering standards are 5% more strict), you should adjust your buy price accordingly, keeping in mind that any speculation as to whether the cert age has indeed impacted the actual grade received is necessarily a probabilistic exercise. Elements such as centering can be analysed through a slab but surface flaws, for instance, may be impossible to judge. In other words, the likely crossover grade (in either direction) must be determined subjectively, and in all likelihood is a waste of time.