trigger question

[charly]

hy!

i want to build a trigger generator around a 555 for several purposes.
i am using the 555-demonstrator software for it. my question is now how
long should a trigger be?
with the software i can change resistor and caps values so that the
output pulse-width ranges from 10 psec up to 1000000 secs. is 10 psec
enough or should it be in the nsec area?
its going to be a monstable circuit for converting a lfo-square waveform
to a trigger-signal  for a sequencer,...

regards, charly