Regarding "stress to the radio's finals", what is the radio's duty cycle?   That is the number and procedure and time limit to follow.   As to power settings, each radio has the correct procedure for setting the audio levels and the power settings based on mode.  There are different ways required based on the radio and the data mode.  All of which are correct.  Each brand and model may be quite different.  I find that it is when hams rely on "old ham lore" to do things that issues abound.   Read the manual and follow the procedure is always the better way. 

In my case, following the Elecraft procedure, I set the PWR control on the radio for the desired operating power.   In the case of running barefoot, I set the radio for 100 watts output.   From my take, there is nothing to be saved by running reduced power.   I do run reduced power when driving the amplifier.    I know many hams operate at reduced power with the idea of "saving the tubes or finals".  Measure the efficiency and you'll find that operating at the rated output is the most efficient way. 

73
Bob, K4TAX