Don't think it will fall apart, just might leak ,eventually. Hopefully your correct. did you get a new rubber plug for the sending unit? That would be Fahrenheit to me 450 F.
The solder they used on that is a low temp solder. The temps for Powder coating reach about 450 degrees. I had mine ceramic coated as the temps in that process are almost half. This is the info I received when I questioned powder coating mine.