I think half the battle is agreeing on a frequency that both of you can live with. The second half of that battle is to underscore its importance. That it should be something that happens, almost without fail, as part of your married life routine. It really took H a long time to see that being tired, or having a sunburn really only got him out of that day. The next day I was expecting him to ante up.
I don't know what I'm trying to say here, except that to keep the dialogue going about frequency, and if she is too tired/stressed for that, then the WWME talks should take its place.

There must be room for marital intimacy of some kind in your R. You can cut corners all over the place in order to accomodate your busy lives but you can't cut that out because it's the cornerstone for the rest of it.

HP