Over an extended length, cables lose their capacity to draw sufficient power, unless they are heavy duty leads, and the premises can supply sufficient power. This also can be subject to a lot of variables.
If they are normal light leads, you could either damage your equipment through low power draw, or blow the fuses in the house, or melt the leads causing a severe short circuit, or all of the above.
Death is permanent.
Most equipment down under has recommended lengths for leads and rated amps per lead.
Also, the advice about uncoiling the leads completely, is very good advice WHENEVER using extension leads.
Cheers,
Shorty.