Stormin:

Here in Canada, refrigerants are treated like toxic waste. You have to have a license to work on AC and refrigeration systems in order to buy refrigerants, and even then you have to meticulously document what happened to the refrigerants you removed from equipment. You can't just buy a piercing valve and "fill er up" like you could in the 1980's. If I have a refrigerant leak, the service tech would have to evacuate the remaining refrigerant in the fridge, find the leak and fix it, re-evacuate the refrigeration lines in the fridge, and then add new refrigerant. The cost for labour is roughly $300 to $400, and any parts (like a new compressor) would be on top of that. It makes more economic sense to buy a new fridge.

Trader:
You're wondering why I want to bother seeing how the frost builds up on the evaporator, and why I just don't chuck the fridge?

It's because I'm old enough to have been wrong in my assumptions more than once, and I don't want to be wrong on this fridge cuz a new fridge will cost me about $400. If I can see that the frost isn't forming uniformly over the whole evaporator coil, then I know it's a weak refrigerant charge, and I have no hesitation to salvage old parts from the fridge and phone a metal salvage company to pick up that fridge. However, I don't feel comfortable throwing the fridge away unless and until I see how the frost accumulates on the evaporator coil.