BJ, compare how many coins and supplies you get from a bronze age building compared to an iron age building. Each age they go up!
However if you advance ages too fast, you run out of resources and can't make anything from your new age. Here's a good idea. Count your current houses, let's say 10 houses. Check the cost of ten houses from your next age. If you have enough resources to build, then advance ages, otherwise stockpile some more. Same thing with production buildings for supplies.
Now about the recurring quests. You get coins, supplies, forge points, medals and goods. Once per age and type of recurring quest you can get diamonds then you get no more diamonds till the next age (and recurring quest type). Each age you advance, the amount of coin or supply rewards increase, but so do costs in coin and supply recurring quests. Costs also increase in 'Spend X Forge Point" quests.
Can you easily satisfy your recurring quests right now? Then good, stay in your current age and invest your forge points in Arcs to get space expansion medals. If it's hard to satisfy current quests, consider advancing an age to get more research space expansions. The game is all about balance. If it's still fun, keep it up. If it's not fun, consider changing it up to keep it exciting.