2017 Yaris USB and oil question

[RutherfordmanX]

First I would like to say thanks everyone for tips with buying the 2017.
OK so I have a few questions. First can you leave a cord plugged into the USB port all the time without any issues. I listen to music from my phone and charge it while commuting so I have no reason to really unplug the cord unless I am required to. Now on to the oil question. The dealer has offered a lifetime power train warranty with the car at no cost if it is serviced per the book by a certified technician. On my 08 I did all my own oil changes using Castrol GTX and at 378,000 miles I was using a little oil but not much. I will be doing an oil change every month and a half with my drive. I am going to look and see what the difference is cost is from doing it myself or letting the dealer do it but do you think it is worth giving up the do-it-yourself for the warranty? Also is synthetic worth the cost since I will change it so often? I understand I may be opening the door to alot of opinions