amp hiss impact on speakers

Tweeters are usually specified as being able to handle many watts, within their specified frequency range. For example consider this datasheet for a tweeter that is used in a very small stand-mounted speaker made by Salk (model WOW1). The datasheet indicates that the tweeter is rated to be able to handle 100 watts when used with an appropriate crossover network that would keep low frequencies out of it.

Since you only hear the hiss when your ear is very close to your speakers it would seem safe to assume that at the usual 1 meter measuring distance the hiss level is **well under** say 40 db. But let’s assume it is 40 db. Given a tweeter sensitivity in the area of say 87 db/1 watt/1 meter, which is the spec on the tweeter I linked to, it can be calculated that the tweeter is producing the hiss in response to an input in the rough vicinity of one fifty-thousandth of a watt, i.e., 0.00002 watts!

The bottom line: It’s a non-issue.

Regards,
-- Al

geez, and I presumed only an SR fuse could possibly extend the life of a tweeter.

Definitely overuse of carbon.

@almarg   Intersting post. On my ss amp, if i listen very closely to the tweeter, even with the amp in the off mode( which in this amps case still is actually in the stand by mode...unless it is actually unplugged from the wall) I can also hear this very very faint hiss. I disconnect the bi-wire cable that connects to the tweeter side in this case, while leaving the bass connection still attached, and the hiss goes away. No issues. 
However, if I were to leave the connection, and I suspect this is what the OP is asking about, the tweeter would actually be playing 24/7. While it is clearly NOT being over driven...far from it, like you stated, the tweeter motor is still active. IMHO, this would lead over some extensive time to a premature aging of the part.