Getting a mbp, questions about ssd and hd for portable purposes

Hello, I'm getting a mbp 15 and I'd like to know how you guys would do to use it when portability is required.

From what I know, with ssd, the best would be to install everything one time and then don't write the drive anymore (or as less as possible) to preserve its performances and reliability...

I also know and always used a second drive for projects, recording

Problem is, with an external drive it is not portable anymore

So I was thinking... What if I use a USB key for recordings? And what if I use another USB key where I would install OS X and boot from that when I want to use internet?

Suggestions?

Thanks