Is there any diminishing return on grinding spices for a "tea"? I'm actually making root beer, but I've found the best way is to boil herbs and spices the same way one would make a tea, and then I add sweetener, leave it to chill, and use a carbonation device to add bubbles.

So far I've been using ready made root beer ingredients that come either in extracts or in bags of herbs, like a loose leaf tea. Now I want to go the next step and make my own blend.

I've got a recipe I want to try and have bought all the ingredients I need in whole form. I'm wondering if there is any advantage in grinding them up. This answer on this site leads me to believe that it's workable to leave spices whole, but I feel like that wouldn't be the case with a whole nutmeg nut. Surely the flavour would not be accessed by boiling water in such a hard and thick nut?

I also learned that in the case of tea, it's actually inadvisable to boil or steep them for too long, as it releases bitter tannins. So I wonder if grinding down spices to "release" more flavour might also have adverse affects.

So, bottom line, maybe you can boil spices whole, but maybe it's better to chop or grind them a little? And if so, how far should one take it?
If you're boiling them it isn't necessary to break them down at all unless time is a factor for you.

Nutmeg also works well boiled whole as you can see in many traditional hot beverage recipes.  However, if you want to be able to add all of the spices at once, grinding some of them is advisable.  Otherwise you'll have to add the spices to your mixture at different times to avoid flavor imbalances.

The finer that you grind the spices the quicker the volatile organic compounds will be released.  In this way you can control the strength of flavor in the final product if all of the spices are added at once.

I've not been able to find any reference to boiling a spice for an extended period changing the character of the flavor(just the potency) which makes sense for a spice since we usually eat the whole thing in ground form anyway.

The same does not apply to herbs.