what happens, when a code sign certificate expires?

[Tiemo Hollmann TB]

Hi,

I just start the first time with code signing on Mac and wonder what will
happen, after my developer ID application certificate expires. Will I just
don't be able to code sign new applications with this certificate, or will
the code signing for all applications with this certificate get invalid from
this point on (what I actually can't imagine)?

Just for my interest, can I create multiple developer id application
certificates within my account (what probably wouldn't make sense), is it
possible, or is there even a use for it?

And what happens, if I wouldn't extend my Mac developer membership one day.
Will the certificates get invalid? I am a little distrustful because I
experienced it, when I didn't extended my iOS membership last year by time,
all of my apps in the appstore where deactivated and suspended from the
shop.

Which Tool do you use for code signing Mac programs? Is AppWrapper a good
choice?

Any experiences or knowledge?

Tiemo