I hate to say it, but you just got lied to by the Managers at that dealership. There is no "required" finance time on a contract and in fact, they broke the law by telling you that. Also, the incentive was probably 1500 or 0% for a predetermined amount of months. Either or, basically. By what you did, you paid very little interest which is great. But that 4 months waiting time? Thats just the Finance Manager making sure he gets paid the reserve from the bank in whatever convoluted way that dealerships pay plan is set up. I understand it made very little difference to you in the grand scheme - but just wanted to set the record straight. Its best to play along with that type of BS as you'll get a better deal that way, but as soon as you get the first note - I'd pay it off.
Believe it or not, leasing is actually the better opportunity right now because car values are so extreme. But thats a different discussion entirely.
Best advice for you - if you're an 800 and above (as some versions actually cut off at 800) - you should really look into some investment opportunities. There is no reason not to have your credit working for you. Simply owning a second house and letting a property manager take care of all the headache bullshit is a suggestion that Im all too familiar with, since my business does just that.
The basic principal for retirement is to take the age you started investing, half it, and thats the percentage you should be putting away in a full time job until you retire. You can probably count on one hand the amount of people that actually put away that high of a percentage, especially with how fast inflation is eating away at its value. Real estate is the one of the only things that actually competes with inflation in terms of value.
But again, Im not a financial advisor.