Yes, you can.
I guess your host/service definition for check you've mentioned have
That will mean 180 seconds. If you want to lower that to a minute just change those intervals to 1.
But if you still want to change to exactly 45 seconds you can do lower example.
In default Nagios configuration (check the nagios.cfg file) there is a variable that says:
which means that every interval efined in host/service definition will last 60 seconds. That means if you have defined, for example:
that notification will repeat after 1 interval = 60 seconds = 1 minute.
Be aware that changing interval_length variable in nagios.cfg will be spread accross all configurations in Nagios, you cannot specify interval_length in service or host definitions, just on a program-wide basis in nagios.cfg.