I kinda had these thoughts too but the missus beat me up. It only takes one senior moment to forget to change the freezer over to mains on a bad day or when going away for the weekend and you've got a freezer full of non-frozen food when you come back...
Not worth the risk (in her book). Especially as I've got a memory like a sieve... 
I once almost burnt down my previous apartment because I put a NiCd pack on to charge (on the same 30A lab supply of course) and the forgot it and fell asleeep. Luckily, the wimpy wire burned out and went open circuit before the battery pack could burst into flames... but it did leave a scorch mark on the carpet where the plastic had melted.
