Part time for 5 months? A person here had theirs left in by accident, hit 70Mph and the transfer case blew apart. If it was constantly WET, snow or ice for that 5 months, MAYBE not so bad, but on dry pavement, that's a no no...
I change my trans fluid every 36K, but, only did it ONCE in the Avenger at 30-some-Kay miles. I had a trans cooler on it, I checked the fluid a lot, was always the correct color, so, didn't change it. I used ATF+4, whish is synthetic anyway, so I let go. No slips, no shift problems, nothing!
I change my Syth oil ever 9K (change filters at 3,6 top off, and then 9) I went 24K miles on the Avenger once using 10W40 synthetic. Syn oil really takes a beating, and I use it in the Lib now as well.
I change the brake fluid when it's brown in the reservoir. I use a spray bottle thing, stick it in, and pump it out. Run it for a week, then do it again... I never, EVER bled and refilled. I could always push all four of the caliper plungers in with my thumbs, so I never needed to change it. No calipers ever hung up on me, nothing. The V6 Avenger I had was the most reliable car I ever owned. Rust would have done this car in WAY before the drivetrain failed on me. Original timing belt, original water pump, EVERYTHING was original at 150K+ miles on it when traded...
Also, In my avenger, I never, EVER changed the coolant - 150k+ miles, nothing wrong with it. Didn't have to change the water pump, no clogs, and no rad build up. The stuff they use is supposed to last 75K or more miles anyway. My water pump was good, at high rpms it would kick coolant out the over-flow anyway, so I was ALWAYS topping it off. Even at 150K+ miles, when at 5.5K rpms, coolant would go out the over-flow. This car did this since the day I bought it, new off the show-room floor in Aug 2000.
I have a trans drain kit I want to install in the Lib, and will as soon as I take it in for the change, I will have my buddy at his shop do it, so I can drain and fill whenever I want.
I will do the same to this Lib, that I did to the Avenger, because it WORKED for ME...