I don´t need to drive any servo, only monitoring 12 diferent servo angles or perhaps pulse width.
In this case the Servo library is the wrong tool to use. It's made exclusively to control servos, not decode the incoming signals.
As to decoding 12 signals, it all depends on whether those signals are coming in parallel (as done by some modern receivers) or sequentially (like for most old style RC receivers) and whether you need to reach each signal at each refresh cycle.
If the second thing isn't too critical, just read each signal in peace and display it. If you add a little logic to your program, you might even figure out an order to read the signals which wastes least time for sequential signals. You even can use multiplexers to connect the servos.
On the other hand, if you need to read all servos at each refresh cycle, you're going to have a lot of work in front of of you to make things work correctly, specially if you have parallel-signals coming in with similar but not equal duration. Also a lot depends on how precise your data needs to be. Are degrees enough or do you need to decode correctly all 1024 steps.