I'm right there with you. I've slowly put on size while staying relatively lean all around the 150g mark. At this point, I know my optimal intensity, frequency, volume, etc. week to week and know that that's as much as I need. I also know that with lower fats I fall apart. Aching joints, loss of energy, issues sleeping, etc.
That being said, don't be afraid to experiment, and don't be afraid of a little water retention. 150 is the sweet spot I found after experimenting with much higher carb approaches. Who knows, you might feel awesome at 300 and stay lean while performance jumps.
One last thing, going relatively low like that I find every couple weeks or so I can get away with a "free" day where I eat what I want within reason. Typically pretty heavy day for sweets and I probably land in the 400-600g range. It provides a nice little boost to training for a couple days after too. Just experiment and be honest with what you see in the mirror and how you feel the next couple mornings.