This would be a great deal of cash savings per device.
This is only true if the quantities warrant it. It costs money to develop a board and supposed you cut down the cost by half then you are only saving 10 * 30 = $300 a year. You have to weigh that against the cost of getting PCBs made and assembled. It is just not worth it at these numbers.
Some of the things I design get made in the millions so save $0.1 on that and it is a great deal of money. Other things, like my current work based project sells only hundreds a year so ten cents is not so much.
There are industrial, commercial and military grades of components and basically they can withstand higher temperatures. For improved humidity performance you need ICs in ceramic packages rather than plastic packages. Also you can get better grades of capacitors with a higher life / temperature rating. This is important because capacitors are one of the things that have a known wear out mechanism.
After that, as has been said before, it comes down to protection in the way of conformal coatings, potting, cases and cooling. For every 10 degrees C rise a unit works at the expected life half's.