My crossdressing is stress related; basically it's under control, but it takes a certain degree of mental 'cpu cycles' to to that. When too much else is on my mind, say, whenever I'm going through any difficulty in life, the ability to suppress the desire to crossdress is more likely to wane, and I dress.
The longest I went without crossdressing was several years when I first dated, and got married. As the marriage went on the rocks, so did my ability to contain my crossdressing.