**No—espresso does not become “dead” or undrinkable after five minutes.** There is no universal time at which it suddenly becomes too bitter.

It does change as it sits:

- **Aroma escapes and crema changes.** Research on espresso found an initial burst of aroma release during the first 2–3 minutes, followed by changes over several more minutes. That supports serving it promptly, but does not establish an expiry time. [Espresso aroma study](https://pubmed.ncbi.nlm.nih.gov/21905723/)
- **Cooling changes the balance of flavours you perceive.** It does not invariably increase bitterness: one coffee study found stronger bitter notes at higher temperatures and more sweet and sour notes at lower temperatures. That study concerned brewed coffee generally, rather than espresso specifically. [Serving-temperature study](https://pubmed.ncbi.nlm.nih.gov/27765259/)

As a practical guideline, **start sipping once it is comfortably drinkable and enjoy it over the next few minutes**. A five-minute-old shot may have less aroma and a different texture, but it can still be enjoyable. There is no useful “minutes until too bitter” estimate across coffees, cups, and personal preferences.

Your barista had a reasonable point about *consistent tasting*: comparing a freshly pulled shot with one that has cooled for five minutes introduces another variable. For a fair comparison, taste each shot at roughly the same temperature and time after brewing. Calling the older shot “dead,” however, overstates the change.