After the Gettysburg incident, the locomotive boiler rules were updated.

Use is based on days used - meaning the boiler has been fired that calendar day. The boiler is washed out and given a basic inspection every 30 days. Each loco boiler is given an annual inspection by the FRA. Based on the ones I have assisted on, it involves removing the throttle to allow an internal inspection. The firebrick and/or jacketing may be removed every few years, based on the inspectors instructions. After the FRA visual inspection, you put the throttle back in and the FRA comes back to witness a hydro test.

A typical weekend tourist operation can operate up to the 15 year limit, running an average of 98 days per year. To reset the 1472 day/15 year, the entire jacket and all flues must be stripped out of the boiler to allow a full visual inspection. Any needed boiler repairs are usually done at this time since it is the best access. The boiler is typically typically given an ultrasonic test to be sure there aren't any cracks or thin spots. Expensive yes - but a reasonable action to help insure safety.

The only locomotive that has been given a waiver under the new rules is the Eureka, which only runs a few days per year.

These rules are only for FRA locomotive boilers. Steam locomotives not under FRA fall under their respective state's rules.