Why regular LED lighting and LED lamps uses heatsinking which allow improved cooling when used in refrigerator and freezer lighting, LED filament lamps uses a heat convecting gas (Usually helium and oxygen) to disperse the heat of their LED filaments.
Are LED filament lamps suitable for refrigerator and freezer lighting? Are they will have longer life in this application?

Maybe not in the freezer because it would probably ice over the filaments or the glass will shatter from shock or something

 They'll be perfectly fine in both the fridge and freezer . LED's are kinda pointless though due to how little they get used , the energy savings will be completely unnoticeable . My fridge and freezer still have the same lamps installed by the factory over 10 yrs. ago .

Our fridge has a [censored] LED hard-wired in, we can't remove it at all 

Leds promise to reach a lifetime sufficient to allow to be hard wired in, so quite significant cost saving on eliminating the sockets and the user removable cover (and the safety aspects of it).
The question is how far they can keep their promise.
But recently I've met a temperamental, crazy flashing incandescent light in a fridge, the real cause is unknown, but it seems to not be the lamp. Instead of a classic mechanical switch, they use some sealed magnetic sensitive switch (likely a reed switch with some triac or so), which is connected by the wire press-in PCB edge connector. My suspicion goes after that connector (the switch module has been replaced with no improvement), but was unable to confirm it.
Point is, when someone puts these things in, using hard wired LED's (well, hard wired anything really) instead of the extra wires and socket can not be worse anymore...