What do you think? The unsolder-ed wires could make a significant difference in long time terms? Maybe the contact of the wire with the pins would deteriorate, due to corrosion, as years passing?

And what is your opinion, everyone, about using connectors in audio signal paths and in power supply paths (use of power connectors here)?

 

My opinion matters not. There is a vast number of reliability reports (usually on the datasheet for the connector) on a huge number of different connectors , pins and sockets.
http://www.newark.com/wcsstore/Exte...orefront/te_amp/Materials-And-Reliability.pdf

The odds that a device will be dropped or have a soda spilled inside destroying a properly terminated (solder or crimp) well-made connector is much greater than that connector failing internally just from age.

I have crimp connectors on machines that are 20+ years old where the electrical connections are just as good today as then. Those signal and power connections are as good or better than soldered connections.
http://cdmelectronics.com/wp-content/uploads/2014/07/MRE_SERIES.pdf

 

Crimp only - do NOT use solder. A properly crimped connection is metal-to-metal and is oxygen free, so there will be no corrosion. If you don't think this is true, just know the the US military will NOT accept any wire connector that is soldered (if you've ever been through a US DOD system acceptance proceedure, you know what I mean).

And @nsaspook, your opinions DO matter! Probably better than most.

 

It's a lot more complex than that.
You need to identify your target market and environment.
There is a reason electronics are manufactured for different markets: commercial, industrial, military.

Is this for hobby, consumer electronics, automotive, industrial, military, aerospace?

What is the environment?
Temperature extremes?
Moisture, vapor, humidity, immersion, condensation, corrosive?
UV exposure?
Vibration, g-forces?
Tension, compression forces?
Insertion-retention force
Assembly, disassembly, repair, service
Size, strength, durability
Metal content, plating material
Plastic content in connector, cabling
Ohmic resistance, current, voltage, AC, DC
Cost, manufacturability
Color, aesthetics

Did I overlook anything?