Starting in Safe Mode

I started (because I wanted to) my MBA into safe mode. Just hadn't tried it before. It took, what seemed, an inordinate amount of time to boot.

I pressed the shift ket at the BONG and released at the spinning gear screen.

Is this normal? Does OS X perform disc read/write, verification, cache handling, etc. that causes the lengthy boot?

New to Mac and just curious.

Thanks.