In the perfect world with a fully funded grant that allows shop personnel to be hired and all appropriate supplies and material to be purchased, the 19 or any other operating locomotive could be returned at 1472 days/15 years to pristine builders photo "showroom" condition. We all can agree on that as the ideal situation.
In the real world I think that a project like 19's 1472 day (and I am making this assertion generically) can probably be pared down to the bare bones essentials required for the Form 4. I, in my infinite ignorance would assume the labor and material for tube replacement to be the highest cost line item, with UT testing and calculations a close second, some limited firebox sheet work and associated staybolt replacement tied with the UT and calculation depending on how much turns out needing done, assuming no thinness of sheets or other condemning aspects are found. In some cases I believe sheet thinning can be compensated for by reducing the legal operating pressure, within reasonable and safe limits. Probably what is more realistic in the current nationwide economic environment is to deal only with the absolute essentials and just maybe squeeze in some general maintenance items that are most efficiently done when the hypothetical engine is partially disassembled. Running gear and appliance rebuilds could be priortized so that each off season a reasonable sized more easily funded project could be done. I am speaking as a businessman, not as a member of SVRR which I am and certainly not as someone in the know at SVRR because certainly I'm not. For all I know maybe it would be easier to get a larger grant for said work than to secure small amounts of annual funding for off season work at any operating museum? Just my rambling personal thoughts.....