Sex is both my favorite grounding tool, and my favorite method of stress relief. I have a high libido, anyway... So even in long term relationships sex tends to be a daily thing for me.
((I do fit the standard 1:5 ratio. AKA Having sex 1/5th as often several years in, as in the beginning. It's not a constant thing. Starts out wicked high with a new partner, and settles into a daily thing in time. That ratio tends to hold true for most people, whether once a week turns into once a month, or daily to once a week, or several times a day to once a day.))
When I'm all triggery, though, that rate tends to kick back up to multiple times a day. When I'm isolating? It goes nil. So there is some fluctuation there, as well.
Does sex help my PTSD symptoms? Yep. Hugely. Again, because it is both so completely grounding... Being completely connected, present, & focused... And because it relieves so much stress. Conversely, I tend to go a bit sideways when I'm celibate. Other forms of exercise help bleed stress, and other forms of grounding help keep me present, but none so well or so completely.