thinkfan.conf:

sensors:
  - hwmon: /sys/class/hwmon
    name: coretemp
    indices: [1]

fans:
  - tpacpi: /proc/acpi/ibm/fan

levels:
  - [0, 0, 80]
  - ["level auto", 72, 100]

This may look like a bad idea, but it actually works pretty well to keep my X230 nice and blissful while doing normal girl stuff (Twitter, chatting). My X230 with its i5-3520M after being repasted with Arctic MX-3 idles at around 45°C and usually sticks around 48°C, where the fan curve would usually bump up to level 1.

As for hot girl stuff, such as C++ compilation, 80 as a upper trigger and 72 as a lower limit for the fan works fairly well. Once the package hits 80° the fan spins up and then it keeps the processor consistently around 77°. What this means in practice is that the fan doesn’t spin up or down during that period of load, just as fast as it needs to sustain that temperature, and then once that load has ended the temperature quickly returns to normal.

As for whether this makes the laptop feel hotter to use, the answer is: not really. The extra heat doesn’t really get to the keyboard anyway, and it’s only idling around the level that it does usually without the fan spinning up and down every few seconds. It can hit the 50s and 60s regularly, but even then it doesn’t feel too bad.

Only when the laptop is sat in the dock does it brush up against a literal obstacle, since Lenovo’s galaxy brain design blocks off one of the vents where the heatsink is, but even then it only ever hit 80° once and quietly calmed down.

As for longevity, well, these machines lasted this long so how much harm could this do?