It's been a while guys, but to make effects longer I believe you would have to find the specific effect's java and alter the line for the time. The effect's already have a 'FinishTime' of -1, which means they should last until the end of the mission or until the java says to stop.
To make effects time out earlier you could try changing the -1 to something like 1000. See how long it lasts then repeat with more time if desired.
If the effect smoke is too dense:
Color0 0.55 0.55 0.55 0.5.............................this 0.5 here on the end controls that. 1.0 = solid texture, 0.5 = 1/2 opacity, and so on.
Color1 1.0 1.0 1.0 0.0
The above lines are for beginging(Color0 0.55 0.55 0.55 0.5) and ending of effect(Color1 1.0 1.0 1.0 0.0). 0.0 is used for the ending transparency so the effect will fade to nothing. The color is set to 1.0s because dark effects in IL2 have a way of looking green or pink when they become to transparent.
One effect might look okay by itself, but put many together and you will have a hard time seeing through them.
Thanks BTW greybeard!