With 16-GB of memory, what is a reasonable limit to the number of open desktops? I don't know what resources are used by adding desktops, but I am certain it is a bigger deal than adding new browser tabs. I've used 8 desktops (across 2 monitors) for awhile. Adding a few more might really improve workflow.

Type of apps I'd like to always have open: Chrome / Finder / Terminal / Xcode / NetBeans / Excel / Word / Skype / MySql / iTunes

Something like having 2 word docs, 3 spreadsheets, and 3 browser instances (each using all the monitor space in their own desktops) would be very useful. Just a quick 3 finger swipe, and I'm ready to start thinking in a new context. I love it.

Maybe, OSX is robust enough, and 16-GB is so much, that I can keep opening desktops until the cows come home?
That is heavily dependent on the apps on each desktop and how you have them all configured (desktop picture, icons, etc.)

I would open up Activity monitor and start adding desktops and see where it takes you.