When I do a spatchcock chicken, it usually takes about 1 hr to 1.5 hrs to get the breast temp to 165-170. I did a low and slow bird at about 250* and I didn't like the texture of the meat. I also brined that one so I'm not sure if it was the brine or the low cooking temps that affected the meat. From that point, I have been smoking the birds at 300-325* and the meat is much better. I don't brine anymore either. I have been injecting the birds with a mixture of melted butter and whatever rub I am using. The meat is always juicy and tender.