Is it becoming more important for career advancement to have more than one MOS?

In the Guard it seems to be. I've seen a lot of people jump from one to the next chasing promotions. I only have 19D and 31B because they were what was available at the time. Now that I'm 15T, I'm staying put.

Took me 3 MOS's to get where I'm at, 1SG (Join to see)

it all depends on the MOS as your primary and the MOS of your secondary, as an SFC I was 68w/m6 and 38b Qualified, when I put in my promo packet, I ended up going back to med unit or turn down the promotion, hind sight being 20/20 should've turned it down and waited for 38b slot to open, its a choice go back to what you don't like or wait for what you do like, advancement will eventually come and not everybody has a chance to be dual MOS'ed, it took me many waivers AMMED doesn't like to loose people