Questions About Speakers

I had a pair of SF Strads which I loved. I relocated to the UK for a few years and couldn't fit them in my place there. I sold them on the basis that, by the time I returned to the States, they'd be 15+ years old. Questions:

1. Is it correct to assume speakers have a shelf life (moving parts, rubber etc) and if so, what is a good estimate of life expectancy?

2. Has speaker technology (carbon fiber, Beryllium etc) improved so significantly that older speakers cannot compete?

3. I replaced the Strads with Kharma DB11s which I like but don't love. I did not purchased SF after being told by some that SF post Franco Serblin was not as good as before. Views on SF post FS?

4. If you have auditioned the new Stads G2, can you please share your impressions?

5. What is a good rule of thumb when trying to match speakers to a given size room? How much SQ & scale is lost by selecting a smaller speaker suited for a smaller room?

6. Any recommendations on speakers that play well with dTZ 18NS & 108 both mark 2? 

Thanks