I've been hearing a lot of chatter about needing a major amount of sentient goods in the latest chapter, and time boosts being one of the only ways to acquire them...pehaps these time boost prizes are more targetted to the advanced cities. although, as they can be crafted and won in the spire quite regularly, I do agree they are not as valuable as when they first appeared in the game.
I recently completed Chapter 15. I didn't use too many time instants, but when I did I used 1 and 2 hour instants on 3hr productions rather than 1 and 8 hour instants on 9 hour productions because 3hr productions give you so much more goods per hour. Although it's too late now I would say that the best prize to go for to get through chapter 15 would have been 10x MM spells. A MM spell gives 50% more goods for 13hours. That's like getting 6 more hours of goods per spell if you did 3hr productions. Ten of them would be like 60 hours of goods. That will give you more goods than 4x8hr time instants which is basically 24 hours of goods. (I know that's weird math, but if you use 8hr instants you need to do 9hr productions. 9hr production produce as much goods as 2x 3hr productions so each 8hr instant gives only about 6 hours of goods so 4x6=24 hours of goods). If you build and upgrade the Elvenar Trading Center the MM spells become even more productive. It should also be noted that using time instants requires that you have the necessary seeds to run the factories for those hours. Increasing production using MM spells does not require additional seeds. I only mention this as something to keep in mind for future events or perhaps if you have the choice between crafting time instants and MM spells.
Because I had lots of Portal Profits I didn't need a settlement for most of the chapter and that left me plenty of space to build 4 T6 factories which, along with MM spells, helped tremendously. But that is not really as many goods as it may seem because in Sinya Arda there is a terrible imbalance of trade for Silly Soap, which is my boost, looking for other T6 goods, especially Shrooms. At the moment I must offer a 50% bonus of Soap to get Shrooms to get a trade taken and that can still take a while. It's very frustrating and this imbalance will last for the foreseeable future unless they decide to offer a building in the Spire that produces Shrooms like they have ones that produce Scrolls and Tree Gum. I'm so jealous of Shrooms producers because not only do they NOT have to wait for trades because the vast majority of trades in the trader are looking for Shrooms, but they typically get 10%-50% bonus on their trades. A Soap producer will need at least twice as much production as a Shrooms producer to make the same progress in Chapter 15 in Sinya Arda. I have no idea what T6 trading is like in other worlds. I recommend building at least 2x T6 factories and more if you have the space, pop, and seeds to do so.