Given that the reason people need to keep them alive is to stay in the FREE tier without the downside - it seems that they would not then turn around and PAY for that to happen.
Big bold teaser text: "alive forever for $9.99"
vs.
Small grey text: "for 365 days at a cost of $9.99"
I use uptimerobot.com for this - 50 monitors for free
Plus uptime robot helps you monitor your site. $10 a year is a steep price to pay for something thats just as easy to do for free.
I would hope people do status checks more than once per hour on their web apps.