If (for example) fermentation ends after 2 weeks but you leave the beer in the primary for 3 is that considered to already be past your 2-3 day mark?
It's actually not that much off-topic.
I would consider this yeast 1 week old since the active part of fermentation stopped a week ago.
While I have been seeing better fermentation times and oftentimes also better attenuation with fresh yeast compared to older yeast I have brewed lagers with slightly older (3-7 days) slurries and they have been fine. I don't have data that actually compares the taste of a beer brewed with fresh yeast to one brewed with older yeast while everything else has been the same.
On a recent Munch Helles life got in the way of brewing the 2nd batch and the yeast sat in the fridge for 4 days, compared to 2 days for the first batch, after propagation was done. The result was that the beer fermented slightly slower and that it had a harder time reaching final gravity. The 2nd batch left an attenuation to attenuation limit difference of 2% while the first batch had only 1% difference. This makes the 2nd beer slightly sweeter. While this works well for a Helles, I wouldn't like this to happen in a Pilsner where the goal is to get attenuation to the attenuation limit.
In the end it comes down to taking good notes. Try to keep track of the age of the yeast and keep track of the fermentation time. For lagers, I take a gravity reading 7 days after pitching and divide the difference between the OG and that reading by 7 to get the average gravity drop during the first 7 days. I also know the attenuation limit from the fast ferment test which allows me to track how well the yeast is able to reach that limit. In most cases getting to the desired attenuation to attenuation limit difference is the hardest part for me. Warm maturation rests, which speed yeast activity, greatly help with that.