If you are concerned about over-heating, a good air-dustering of the interior, and a hoovering of the air vents may help.
While you are there, check that everything is seated correctly, no loose cables.
Also, ensure that there is plenty of space for air to circulate around the case, especially near the fan outlets and air grilles.
Saying the temperature reaches 30º doesn't tell us much - the temperature of what? GPU, CPU, HDD?
If any of those are only at 30ºC I would be very happy!
You might also consider installing additional fans, or larger fans, in the case.
In terms of wear on the components, HDDs are probably best left running rather than being switched on and off. Assuming that the PC isn't also doubling up as an oven, of course.
SD