It lives past tent 15, past the frog, and past chapter 12.
Note: I am not a competitive tourney player; I'm content with 5 rounds of 20 provinces and a score of 3-4K.
I think this is a bit misleading, especially when talking about AW's. Other things in the game are based on the number of AW levels; the biggest being divine seeds (that decay). Players need them in Ch11 Halflings and in increasing quantities going forward from there. They're needed to make sentient goods (that also decay); they sorta replace the supplies used to make standard goods. This hits players who use diplomacy and cater heavily the hardest. Mana needs will also continue to increase, and I've seen players get into trouble with mana when they replace/upgrade mana event bldgs with those same bldgs that make seeds at higher chapters. Willows are just too big to be effective; there are better regular mana bldgs going forward but they are not nearly as good as event bldgs. Players do get the Dragon Abbey AW at the end of Ch10 that can produce mana on demand if they have a big enough inventory of spells to cast at will. But, again, that increases the number of AW levels as it is upgraded to get more mana/spell as well as needing space (20 squares of an expansion). The only regular bldg seed source is the bonus seeds available from the Trader (they top out at 3hrs, so collecting every 3 hrs increases your inventory more than waiting to collect past the 3 hr mark), the only other regularly available seed producer is the Festival Merchant in crafting. The mana production of that Merchant is also good, but will be lost if the space is used for higher level Merchants for seeds. More expansions will be needed to keep the old ones and add new ones. The amount of seeds from the Trader depends on the number of AW levels; the more AW levels, the more seeds with each collection. Choosing to have fewer AW levels will hamstring a player especially if they need sentient goods for catering/diplomacy.
As far as the frog for combat players: he comes on board in late Halflings, but is pretty squishy at 1*. He may be more viable for humans at 1* as their mortars are pretty weak, but for elves Golems are a better choice. He's decent at 2* (gotten in Ch13 Amuni), and with his range can be used in certain battles with better results than the 3*Golems, but it's not until he gets to 3* in Ch15 that he becomes the powerful unit that most advanced chapter players are talking about. Don't get me wrong: I love my frogs! But, I did fine before they were introduced. Note: I only play as an elf.
Am I doing what I'd like to do in tourneys/spire even with the current structure for increased costs? Yes. Do I dislike the introduction of a structure that penalizes growth/progression in a city building strategy game on the principle of the idea if nothing else? Double yes! Also, my own perception is that it disadvantages the non-fighters the most. I know several, one of whom I've been in an FS with for 3 years. That's where I've witnessed the struggle of players who have a different style than myself. To preserve their sanity, many end up choosing between the Spire and the tourney. This keeps them out of either a Gold Spire or a 10 chest tourney FS that has weekly minimums depending on their choice. They certainly won't be able to carry their own weight in an FS that is both. They have chosen a hard enough path that it seems especially unfair to hobble them even more.