I exhaust to control humidity.
Humidistat and thermometer controlled exhaust.
Saves power, and lets the plants transpire more naturally, rather than in negative air pressure all the time. Adds a bit of stress from what I have seen.
I use speed controls to balance out the intake speed and the exhaust speed.
Filtered intake.
6" in 6" out in a 4x8
I try to keep it as sealed as possible.
Keeping an ideal environment as is without venting. Of course it does, so the intake/exhaust fans are the buffer to control it when it does get above set relative humidity and temperatures.
I couldn't tell ya if having them turn on and off will or has affected the lifespan of my exhaust fans.
It's been like this for 4 years and all is well.
I don't like the risks of venting outside so I try to keep it minimal.