The custom menu function that came with 3.o is cumbersome and time consuming if you want to use short navigation
I'd recommend that you modify the Menu area to include an option there for each menu item. Such as... Check here if you want to rename the Page but keep the existing Navigation Label the same. That way the Label on the Navigation bar would not change when you changed the Title on the page and the new longer Title would not be seen by visitors for a short bit AND you would not have to go back into the Menu area and change the Navigation Label.
This are the steps I used to create a custom menu so that I could keep short titles in the navigation area and use more keyword-rich and SEO-friendly titles on the Pages:
1. Created a custom menu and by default the short titles were the same as existing short titles.
2. Went to each static page to re-write a more keyword rich and better SEO title. - the problem is that as I did this, each longer title appeared within the Navigation Bar. I would have to then quickly save it in the page setting, go back to the Menu area and change the now longer navigational label to be a shorter label.... actually, change it back to the shorter label that was there before.
I call this a "glitch' because site visitors would see a longer navigational label for a minute or two as it was being converted back to the shorter label..... AND it is wasted time to have to go back and make changes.
I am preparing to rearrange the menu/submenus on another site with about 30 pages and using this process I described above will take a much, much longer time as there are more pages to work with.
So, I hope you bright and talented folks at WordPress can make this process more efficient.