Hey matie,first of all welcome to this jolly bunch of potheads!! May i ask,what hood do you have? If you have an Aircooled Hood you should not switch the fan off at all as the heat in the Hood would melt the cables even WITH protective wiresheets around it!!Happened to me 3 days ago and luckily i smelt the burning thing early without damaging my HPS!! If you don't have a hood and just have a reflector,get one fan oscillating for flow and one just blowing the heat away from your lamp straight towards your fan that sucks outwards! I have the fan on 24/7 regardless of stage,seeds,seedlings,veg or flower!!Humidity at night goes up to 66% now on the 12/12 and the dryfan does nothing for that to drop,just ventilates the branches and flowers(or flowers to be) enough so water doesn't form in/on the leaves/flower/pre-flowers!
That said i should take into account that the strain i am currently growing in my hydro is the Church and GHQ claims it to be the most mold resistant plant!!I say it will show in flowering...Good luck and happy growing matie!!