AVR-Chat

I know this isn't anything about uC's but I have a general question
regarding toggle switch ratings, and there seem to be a lot of very
knowledgeable people on this list.  Typically a data sheet rates a switch
for, say, 125 VAC, 250 VAC and 28 VDC.  My applications, however, are
typically 12 VDC.  Can I convert the 28 VDC rating to 12 VDC using a same
power equivalent, ie, if the 28 VDC rating is 4 A, then is it ok to run the
switch up to 28/12 x 4 = about 8 or 9 A?   Thanks, Steve