this is my view point on the subject (i forget to put that on my 1 post x)
only the brige can active or deactive (self-destruct), now the timer for the self-destruct (math a head). time need for the crew to evacuate (EEV) the ship in normal condition x2 plus(+) 1min per deck
a*2+(b*1)=timer
now let use a big ship ex: a 7 decks warship(b) ,4min to run for the EEV and evacuate (a), 4*2=8+(7*1=7)=15 min
smaller ship 2 desks and 1.3min for the EEV = 1.3*2=3min+2*1=5 min
ship whit no EEV cannot have self-destruct <-----for balance maybe ?!
the timer can be stop any time before half the time a pass (need to wait 2min to turn on again)
after half(50%,1/2) time as pass the timer become lock=cannot be stop (turn on/off) but can be disable(not working after need to be replace in shipyard,... ) stop ppl to abuse the timer now you have consequence.
Hull seize also effect the timer ex: mining base
