Basing mechanics on time instead of number of raids hurts
In a game like this where things are so irregular, basing mechanics like Boosts (and Outpost lifespans) on time instead of number of raids sucks.
For instance, some of my bases aren't getting raids. I'd really like to try out the Metamorph's Boost to increase the amount of Prestige earned, but... the bases aren't getting raids. They can go for hours and hours without getting a single raid. So what good would the Boost do? A 20% boost of 0 Prestige points is still 0. Activating the Boost for an hour while not a single raid occurs would be a waste of the Cells I am constantly struggling to earn (needing Cells for almost everything makes buying/upgrading slow to the point that I'm starting to feel bored of it, this is a painful artificial cap on progress to keep it at a snail's pace).
Anyway, the Metamorph's boost is kind of callous to Builders. "Oh, you're not getting raids and need a boost in Prestige? Well, here, have a boost in Prestige for an hour during which you're likely to continue to get zero raids, just like the six hours that preceded this one."
All of the Boosts are based on time, but you have no idea how long it'll take to complete the next Outpost(s) you raid, no idea if your own Outposts will get Raiders. For Boosts that increase the output of both Raids and Outposts, going by amount of time makes sense, it'd be difficult to designate it otherwise and the gamble is more likely to be worth it, but otherwise the gamble is a currency sink with little to no reward in a game that's already super grindy.
Using time over number of raids really only works if things are moving at a fast or even consistent pace. But they're not.