It's a matter of expectations and requirements.
There are some free hosts (though they seem few and far between these days) that are trust worthy and reliable. If you can find one, great (I can certainly suggest a few). Now what do you expect from them? Well, they need to be funded, so you're likely going to have ads or some other requirements to meet - that's not a bad thing for something you're getting for free (if it's a good service)!
The problem many will have with free hosts, if something does go wrong, you haven't really got a leg to stand on. Most will still help to resolve the issue, it's just part of the parcel of free hosting. If you want to hold someone accountable for downtime, then you're gonna want to go with paid hosting that has some sort of compensation for downtime/issues and maybe a good backup offering.