I dealt with my infestation during spring. The smell lasted about a week, after which I got two hatches of bluebottles every day for a week or so. I used elementary biology to interpret what had happened to the cadavers.
I got infested once (well, my garage then basement then house did). I tried humane traps to no avail (They came back faster than I could transport them to another place). I tried spring traps to no avail (they proved expert at getting the bait without suffering a crushed skull). Then I reluctantly put down glue traps (which require one to figure out a humane way of ending it for the trrapped animal). When I caught and euthanised my eleventh or twelfth mouse I gave up and called in the pros, who put down some sort of poison with the singular property of making the doomed mouse very thirsty. I was advised to check the bath before showering each morning. That did the trick eventually. I imagine they died in the crawl spaces, but I didn't notice any smell. Perhaps the corpses mummified and now await discovery (whereupon they will doubtless put a curse on their discoverer). I don't think I'd waste time with traps if it happened again.
[SM] That sounds very similar to the situation at my old flat; I tried traps and poisons, none of which worked. But then Dave came round and dispensed the hard stuff, and never a squeak after. But that was a modern flat, and filling the holes with expanding foam was straightforward. After our first visitation we called Dave in straight away, and it took him three attempts to get rid of the first batch; and expressed doubts that given the way the plumbing had been done in the kitchen that he could offer anything like a permanent solution.
I caught one of the little dears in a humane trap some weeks back, also using peanut butter. He died in it anyway, for reasons that aren't clear to me. He was only trapped overnight, perhaps six-eight hours, so it presumably wasn't hunger or thirst. A broken spirit, perhaps?