In NPM, when you set the device status via ICMP instead of the slower SNMP, a device still might shows as up, and the last polled data is being showed on the web page. This can be confusing if, let's say, a server when in passive mode doesnt reply to SNMP.
I suggest that after a configurable number of missed polls, the devices still shows up, but all polled data is grayed out to indicate that those values are outdated and might confuse the user. This way we would still get the last polled value if this of any help (usefull if the server froze and no HD space was available), but gives a major hit to the user that this is to be fixed (or not).