This is true. There's no point asking the members here if the desire goes away, it obviously hasn't for them.
But, what of the tens of thousands of people who joined here over the years and who no longer come around. Some may have transitioned, some may have become bored with the forum and they may still crossdress (like my SO). And some have passed away. But I bet there are thousands upon thousands of people who don't dress any more. A friend's husband (in my town) came out to her decades ago. They were deeply involved in Tri-Ess at the time and he even did some pro-bono legal work for them. The crossdressing was cyclical over the 25 years, with periods of intensity where the husband wondered if he wanted to transition, to less intense times, and back to intensity again. There never were any purges because my friend accepted. Their kids knew. Their church community and friends knew. And then he just stopped. Cold. Hasn't dressed in seven years. He doesn't see the point any more.
I think that a crossdresser will only reach that point once he has achieved complete freedom and has gone out at will for years and years. I guess it's hard to stop as long as there is some form of repression (a wife who doesn't totally accept, the need to hide from the kids, living in an area that makes it hard to dress, or living with any amount of internal angst about it), and so as long as these conditions exist there is a need that never really becomes satisfied.
Also, some people just can't get away with dressing in public and dressing alone at home can get old. They cannot pull off blending in, it's hard to keep trying if they feel stared at constantly and so eventually they give up, if they cannot bring themselves to stop caring about what people think.
I think it's wrong to assume that every person who has crossdressed will continue to do so all their lives. Some will, and some won't. YMMV.