This is a bit of an odd one, I've got an old Skinny SIM that I've used in a PocketWiFi in the past (main purpose as a 'oh no, the power is out, time for mobile data' device/SIM), but not used for just over a year due to better data packs/etc for my main phone.

I'm in the situation where if I login to the Skinny site, I still see the info about the number that was attached, but it says "Last top-up 24 June 2014, SIM cards expire 12 months after last top-up", but it seems the network still allows the SIM card to connect (not my past experience with network-killed SIMs - looking at you VF ;)).  So I'm left with a SIM that should be dead (maybe it's execution is queued?), that doesn't appear to be dead.  Is it actually effectively dead or is there still time to top it up.

I'd pop it into a phone and see what happens when I try to access any of the menus but that'd involve breaking the SIM down in size.