How can you evaluate if a component is going to have a long life (manufacturing)?
Ultimately, you can't.

Some manufacturers have a policy of supporting chips into the future, and assure customers that they will be available until a certain year, or that you will have (say) 5 years' notice of withdrawal. That's better than no assurance, but if they go belly-up, then a notice period becomes meaningless. 

If you can estimate how may PCBs you will make, and can afford the stock, then you could make a one-time buy. This is rarely an option. If your market suddenly exceeds your expectations, than that's a 'good' problem.

Ideally, choose chips that are available from several manufacturers, to the same specification. The chance of them all going belly-up at the same time is small, but the chance of the market changing and causing them all to withdraw for economic reasons is higher. Of course, there are a huge number of 'interesting' ICs that are only available from one source.

You can have an obsolescence plan, to minimise disruption if you lose supply of a vital component, to allow you to mitigate its loss fast. Depending on what it is, write it in C rather than assembler, write it in VHDL rather than a graphic design tool dedicated to the supplier, have extra space and extra power available nearby so that if forced to replace it with components on a daughter board, you're not forced into a bigger re-design. 

It only tends to be the military who want 30 year repair or production life. The way 99% of other people work is that a new model of the end equipment (which needs newer components to be designed in) is needed before the components that make up the old one become unavailable. It's a risk, but alongside all the other business risks, most people don't get stung by it.