i would like a balance between both of the above. there are pro's and con's to each, and i have faith in the devs to get that balance right.
one time bonuses i think are great for games as a reward for completing something major. 100 ships sunk, 1,000,000 damage caused, gold earned etc.
there is a sense of accomplishment in hard to earn achievements, and gives the player something to strive for. and finish in their own time.
as where the time limited achievements seem to add hostility to the game if someone can't complete it on time.
(something that happened in WoT and WT causing mass rage in chat over damage and kill steals, and i'd hate to see that element creep in here).
on the other hand, these daily/monthly rewards can help the more casual player make some sort of progress.