I think it’s some kind of bug which may or may not appear. I tried twice: Logging off right after I got the lure and it seemed the only time the counted of the decay was the seconds while I was in loading screen to get back in the game.

After second attempt ( I got myself limit of 3 minutes off) it all seemed well, about two and half inutes went off the decay timer when I got back in the game.

Hard to tell for sure, I got my first lure today, so I have no idea if it is already fixed for good, nor do I know what it works for someone and someone not.