I think in version 2 host checks can be done on a regular 5 minute interval, or whatever you set. But why did you "removed 'check-host-alive' from all host " That's a big mistake. For HOSTA which has 3 service checks done on it, if the service check fails, then we want to know if the host is dead too. So please don't REMOVE the host check. It's important. Just because ftp is NOT running, then you will know if the host is dead or not and can fix it remotely, or whatever. I see that the service you are checking is "ping" and that the host check is the same thing. But in the future, as you start to progress, there will be tons of services that you will be checking, and you may want to define a host "check_command".
This is from the docs...
"check_command: ...If you leave this argument blank, the host will not be checked - Nagios will always assume the host is up. This is useful if you are monitoring printers or other devices that are frequently turned off.
In certain cases, by not defining this, it may give you a headache. Example: Switch1 connects to switch2(so switch2's parent host is switch1, in the hosts.cfg file). If I define service checks for both switch1 and 2, but don't define HOST check commands, then if switch 1 dies, then I will get a page/email from nagios about both switch 1 and switch 2 being dead. But in fact, switch 2 would be "unreachable" and I don't get "unreachable" emails. Nagios could not tell that switch 2 was unreachable, since it is assuming "host's are up" This host is NOT up, but simply by you/me not defining "check_host-alive_ check_comand, it is ALWAYS assumed up. In other works, please define a host check command for all host's. It will give you headaches later on, when you have 298 host's 1071services and are getting 200 emails or pagers just for ONE host being down, and a 199 host's unreachable(of which, you don't want). YOu want ONE email, telling you what is broke, and that's all.
You can force the check by disabling/enabling the host checks by using the external command link "Disable checks of this host" and "Enable checks of this host".