Feed on 1 breast

My lactation consultant said to feed on both breasts for 10-15 each feeding. But it seems like my son wants to feed on 1 breast for more like 20 min. I offer the other one but he is either asleep or full. Is it ok to just feed on 1 breast every 2 hours? He is 2 weeks old.

What do other moms do? Will my supply still stay up with feeding just on 1 breast?