I don't do AOS for X at all - in fact I don't even talk to him unless he talks to me. I offered him a coffee once last Christmas when he was out shopping and was cold, but that is the only time I've ever initiated anything in about 20 months.
He left me so I feel really strongly that if he wants me back, he will make moves. If not, then not. I can live without him.
It does come across as pathetic, esp. if I were to run around after him.
If you're not there all the time and don't show so much interest, the WAS will make more effort.