I wonder how long these train-sets will be in revenue service.
Also, how long is a typical electric locomotive expected to be in revenue service?
You may still be looking at the wrong end of this thing.
When the shiny new Acela IIs enter service, costs will drop substantially. Capacity will increase enormously. In Year One, revenue will be much higher, costs will be lower, and the net -- call it what, "Operating surplus not counting a lot of stuff" -- will be a lot more cash money in Amtrak's hands.
Until they are retired (technologically obsolete or worn out, or for various other good reasons), the Acela IIs will continue to spin off operating surpluses from Year One, which could be 2020, to Year Last, which could be 2050.
Due to the time value of money, the operating surplus of each future year is not worth the same.
The operating surplus captured in Year One is worth the most. The surplus funds can be immediately reinvested in other projects -- let's say various capital investments, from longer platforms and more ADA compliant stuff like elevators, to new and added track, better signals, bridges and culverts, tunnels, etc. The new capital investments will themselves cut operating costs and/or add speed and capacity. They will each offer a return on investment over their useful lives, which could be 30 years, or 100 years, or 10 years. And the additional funds from Year Two will also be invested, and Year Three, and so on.
Any operating surplus from the Acela IIs starting in 2020 will improve Amtrak for many years to come. But any surplus from Year Last, the year before they go to scrap, will not have so much of an effect, because investing that money can't give so many years of returns in the time frame of the living.
Of course, the time value of money can most easily be understood in personal terms: If you inherit money this year, you can use the funds to pay for college, pay off student loans, eliminate that credit card debt with the 16% annual interest, make a big down payment on your home so that future monthly payments are smaller, stash some in an IRA for retirement, and so forth. Or, you could wait another 30 years for Grandma to die and leave you the inheritance. The time value of money says that sooner is almost always better. Long life to our Grandmothers notwithstanding. LOL.
Another aspect of time, of course, is that over some period we are all dead, so better to grab what we can while we're young and able, because tomorrow ...
That now is better includes Acelas and Acela IIs, which could become technologically obsolete in ways we can't quite imagine today. But we have seen very rapid change in HSR equipment since the first Bullet Trains and TGVs.
(I'm not sure that the standard 30-year lifetime for a regular electric locomotive that you asked about actually applies to HSR, which aren't "typical".)
btw The financing deals can be set up using a standard 30-year payback, like a home mortgage. So Amtrak buys a bunch of equipment, say, 70 electric locomotives, and it must set aside, on the books, millions of dollars toward the yearly "mortgage" payment. In fact, Amtrak benefits over 30 years because the yearly savings from lower costs and higher revenues may actually be much, much more than is booked for yearly payments. The savings can actually pay off the cost of the new equipment within 6 years or so. In effect, this plan allows Amtrak to use the borrowed money for other needs over the remaining 20-some-odd years.
So I'm back to saying, the shiny new Acelas -- faster, lighter, safer, cheaper to operate and maintain, with greater capacity per trainset and more trainsets -- will have a very great impact during the first 20 years of their operating lives. After that, who knows? And why worry so much?
If we're so smart as to see the future -- like how Acela IIs will fit into the world 20 or 30 years or more ahead -- we shouldn't waste our genius insights on blogs; we should be investing on Wall Street or in Silicon Valley start-ups, getting very rich now, and not waiting for 2050.