1st timer here: Do I need constant air exhaust all the time?

I have one end of my air-cooled light w/ glass shield open to draw air. My temps have been staying around 79-81 without having my exhust fan turn on for about 4 hours. Have a couple of small fans moving air. Do I need to have another source of exhaust for fresh air?

Thinking of putting a small exhaust fan in top 4" flange. But do I duct with my fan that is for the light, before or after the fan. How about a pre-wired thermostat for the 6" fan. Just trying to come up with the right combo. Thank you..................
 
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