The plot above shows the switch-on behaviour. When 13.8 Volt is applied (upper, grey trace) it takes about 2 ms until the output reaches 24 Volt (green trace).
I use this DC-DC converter on several SMA relais since about 2 years now, none has failed so far. As a test, I put one converter on a 10 Hz square wave generator and let it switch a 24 V relais on/off a whole week (abt 6 million cycles). It survived this treatment as well.
The picture below shows a DC-DC converter mounted on top of the SMA-relais which it is switching.