Four dates decide the quote
Roof, electrical panel, plumbing and water heater. Carriers ask for all four on a non-owner-occupied property and some decline outright above certain ages. An owner who does not know them is quoted defensively, and a defensive quote is always the expensive one.
Certain systems close the market
Some older electrical and plumbing types are declined by most carriers regardless of condition. That is an underwriting position rather than a judgment about your property, and knowing which you have tells you whether a quote is going to be straightforward or a search.
Updating is sometimes cheaper than insuring around it
Where a system is the only thing limiting the market, the cost of replacing it can be recovered in premium difference faster than owners expect, and it removes the annual uncertainty at renewal.