How to protect (not wear out) headphone jack on Mac laptop ?
 

I have begun to do some daily workout routines that play on an external DVD drive hooked via usb hub on my mac laptop.

for this, i have to unplug my headphones from the headphone jack on my laptop to hear the instructor's directions through the laptop speakers. It would be too awkward to have my headphones plugged in to the mac, & in my ears while trying to do exercises. i also have to because, the jack has to be free, with nothing plugged into it for the sound to come out of the laptop speakers.

I also frequently listen to other content on my mac, that I dont want coming out of the speakers, as this may wake family, & dont want others to hear everything I listen to, (not that it is bad) it's just a matter of privacy & consideration. i know i could just turn down the volume, so others dont hear easily, but then it is hard for me to hear, hence the headphones.

i also do not want to wear the headphone jack out plugging & unplugging the headphones for each use everyday. Any ideas for a workaround? or am I just being too fussy with my laptop?

I don't think this is an issue. Not for a stereo mini plug. It's not as fuzzy as other connectors (USB, for example).
You're fine. No worries.

I have a mini stereo plug on it now, but I have to unplug it as well from the jack to get sound to come out of the laptop speakers, does it matter that I plug & unplug this every day?

Stereo mini plugs, both male and female parts, are fairly robust.
Just don't push the plug in too hard, as that could ruin the connection on the audio card inside the computer.
Be gentle, and you'll be fine. Don't be a brute.