"Roberto Quijalvo" wrote in message news
Why replace them if they're working?
To find something more reliable.

How do you measure/compare their reliability ?
How can you be sure you do not replace something
reliable with something less reliable?
Just because switch is non-mechanical in a simple
sense does not necesairly mean it is more reliable.

Just because they haven't failed yet,
doesn't mean it won't.

It also does not mean it will.

There are countless tales out there of failed mechanical switches.
I don't have to personally experience the failure to prompt a change.

I would rather protect myself from the failure and build some
extra flood protection (one more, emergency top switch)
than to worry about replacing the current set if it is working.

Of course, that's not to say that the non-mechanical switches may not
have their faults too.

Then you realize this... ok, let's go back to my first question then :-)