I've never set a hard time limit on the trance's duration. The longest he personally has ever held a trance over someone was a little less than an hour. The trance's duration and strength isn't static; theoretically, it will grow stronger the older Alex becomes and the more he uses it. I think, in the scope of this game, the latter would have much more of an effect than the former (unless we get a time skip or summat.)

It does not weaken under prolonged eye contact. It holds for however long Alex maintains it. When he first started using it, he had to maintain eye contact to maintain the trance. After nine months using it to hunt, he was able to maintain the trance without being present.