In order to build Cloud Castle and to meet the prerequisites (Citadel and Castle), I need to spend 3 days of building and pay 29.000 gold, 36 wood, 36 ore, 20 gems, plus the Titans themselves aren't free. It takes time to build such money up, and there are many more ways to use it -- it referring to both time and money. I can buy more Genies, build my Institute of Magic fully, or, if I find another town, invest in there. By the time when I can afford Titans I most likely already have a handful of Genies and am able to pretty much finish the campaign, I will have to wait for building them, then transport them, then walk with them (they are slower than heroes, hence I do less in one turn).
In a normal game Dragon Golems seem to be worth their money, but... I can't build Dragon Golems in the Order campaign.
Should I actually try to build the Titans in Order campaigns, or is the money better to be spent on something else?