it depends.
I was mulling over this recently with VSL Synchronized Solo Strings. What I finally came to is that its not practical to have one all-encompassing expression map that covers all articulations of the instrument. you can make one like that but then the piano roll will use more space for the expression map lanes then it does for the notes. I think what is practical is to create maybe one huge master expression map, and then when you're ready to work, remove all the slots from the expression map that you know you won't use on that project.
or... Just create each expressionmap ad-hoc as you go on each project. If you're composing along and decide you need a certain articulation for the work, instead of adding the needed keyswitches to the track, add a slot in the expression map and add then use the expression map lane...so that in each project, you will be using a customized expression map that fits the needs of that particular project...you most likely will not need all 30 articulations in any one given project...might be a dozen or so...
The other thing you can do to consolidate your articulations a bit, is as jamwerks said, you can combine expression maps with normal CC automation lanes. The goal is to keep keyswitches out of your actual piano roll... So some instrument controls actually make more sense to just use a CC automation lane to control them. If you think about it, expression map lines are kind of like CC automation lanes...but they are just capable of sending NoteOn events instead of CC events. So if some aspects of your instrument are controllable via CC...it might make sense to use CC automation..particularly if its not an instrument feature that needs to be note-by-note.
The ExpressionMap groups feature (the four columns in the expressionmap editor), can also be used to consolidate your 30 articulations into less lanes. But this only really works out well if you have isolated groups of mutually exclusive keyswitches in the instrument.. and programming an expression map with multiple groups can be a PITA because of the lame editor Steinberg provided until now. This can be complicated to understand and setup, but can sometimes reduce complicated combinations of articulation modes into a much smaller set of expression map lanes that are easier to use while composing. But its a lot of work to setup and not always even applicable for many instruments.