I think that I've done this before and set an alarm not for so long so that it will be an indication that I have to stop. And this isn't just only for the slots but also for other games that we'd like to play like crash, dice, etc. I agree that it's way more relaxing to have a time set and it won't suck out most of our time and will keep us a healthy and responsible gambler.
It's a good strategy to avoid becoming addicted, whether it's setting a time limit or budget, some games are really cool and engaging. Every day people play them with the hope of being the lucky one of the day, I hope to be one of those, although I play very few slot games and etc.