Well, the value of Tdamp informed in the manual is just a guideline that, I guess, is there so you can see an actual thermostatting effect during the simulation time, and to let the thermalisation time be short, so you can see the NVT evolution.
However, I can think of many situations in which being too careless about the Tdamp value will turn into sloppy (and even plain wrong) thermodynamics. So my advice would be to play with it a bit and find when you can get decent evolutions out of it. Definitely, 100 timesteps looks like a good starting point, but you should never jump in with both feet in ANY wannabe NVT ensemble in molecular dynamics.
Pablo