Hi Syl!
The stock tires on the DT300i are Kenda 120/80-14 rated 58S on front and a 150/70-13 rated at 64S.
I've bought Kendas before, and they are good, quality sausages that are reasonably priced. Plenty of good tread, nice, stiff sidewalls.
The part you are concerned with would be the rating numbers - On this tire it is the 58S and 64S:
58S: Load index - 520lbs / Speed rating 112mph
64S: Load index - 617lbs / Speed rating 112mph
Pretty stout tires considering the vehicle weight and top speed! As for wear - That is definitely a tour milage may vary thing. Some compounds definitely wear better than others, but road condition, speed, and temperature play a HUGE role in tire longevity. So any wear estimate you get can easily be +/- 10k miles.
In short - The tires are SAFE. The tread wear? We'll find out