Low and slow more often than not means I use one of the WSMs which is not fited for CI grates.
If I am doing Low and Slow (banked coals method) on a kettle, I do NOT use my Char Broil CI grates. Here is why:
1) There is minimal if any 'heat renetion value' IMO. If you were to try to quantify it, I would say it is something like 6 briqs worth. Does it matter that much?
2) Low and slow is ever so slightly more messy, and would leave debris on my CI grates which would have to be cleaned off. When using CI for high heat, it is pretty easy to give it a nominal brush at the end, letting the heat take care of the work.
3) Most importantly .... No access to the fuel when using my CB CI grates once the meat is on. With the flip up metal grates, in the event I need to manipulate fuel, I can use the flip up grate access.
Of those, number three is by far the reason I do not use CI for low and slow. It is easy to have a door on the off chance I want to move a coal or add a chunk of wood. Let me state, I LOVE the value of my char broil CI grate, and would recommend it in a heart beat if you can get it for whatever is a good price in AUS. I got mine shipped fr under 25 USD which was a 'grate deal'.
YMMV and all that.....