Maintenance required lights and check engine lights are what I like to call "Idiot Lights". I am not calling you an idiot, but rather as the owner and mechanic of my own car, I see those as the car telling me "hey Idiot, you missed something." The point I am trying to make is you shouldn't wait for those lights to come on, you should strive to catch them before they turn on. This extends the life of your vehicle. I change my oil every 5,000 miles. My car currently has 215,000 miles, and runs like it did the day it rolled off the showroom floor, so my idiot light method is proven to work. As for the expense portion of this, if you are driving a 2012 corolla you should easily be able to afford a $30 oil change every 5,000 miles. This is easily saved for, set aside $6 every month for an oil change. They can't sneak up on you, because they are required roughly every 5 months. Surely you can save that. If you cannot you should be driving something much cheaper than a 2012 corolla.

An 2012 corolla uses synthetic oil. It can go longer than 5000. The light should come on at 5000 though it might be ready to soon. If not change the oil at 6k.

I depends on the more miles you travel between oil changes means you'll lower your maintenance costs over the lifetime of your car, but some people challenge that a less frequent oil change leads to other car problems that will result in expensive repairs.

Long trips, steady speed highway driving is pretty easy on an engine, and on oil. 3,000 miles, which is the interval on your sticker, is more frequently than required.

You're at 5,000 miles now, though. That's at the upper limit of what I was going to recommend. It wouldn't be a bad idea to get the oil changed soon.

When its a Fresh oil change do a Re tune up on the Next 3,000 miles

refer to your owners manual. newer car like that, if your putting regular motor oil, then around 4k to 5k miles in between oil change. if your using the more expensive synthetic oil, then 7k to 8k miles. if you don't know when the last oil change was then i would go ahead and get it change at your earliest convenient. just so you know when it needs next time.

you should check the manual for correct info as they are the one you have to answer if there a problem with proof you followed there program

So I bought a used 2012 Toyota corolla LE with about 36k miles maybe 2 months ago. I drive at least 120 miles/weekday on my commute to school (highway speed of 70mph max) and brought the odometer over 41k so far.

The sticker on the corner of my windshield says my service was due after 39k miles but no indicator light has come on yet and I haven't had the time (or money) to do it yet.

Should I just wait for the maint. Required indicator light to show up before changing my oil? Or am I better off changing it when I get the chance?

Thank you for your advice