i run at about 30-40 idle on my computer, room is about 70-75 in this room, in game i get up to 60C, i think 30s-40 is pretty good for your computer tbh. iv had mine for about 2 years, so my thermal paste is most likely Old and needs redone lol. i think youre safe
oh PS, put your side's back on. Open Computer = Dust and Dirt, Closed = very little dust, very little dirt. so in the end you dont get your Fans all dusty and it doesn't slow them down, so you dont heat up! put them on, run your Pc, check the temp, if you dont like it (if it gets higher) take them off. no harm done. just a thought tho