Each game goes a bit different, generally I get long-ish peace intervals around late classical/early medieval and late medieval/early reneissance.what do you do from the middle ages onward?
Usually both not boring, as there's plenty of tiles to be improved, units to be upgraded/replaced, borders to fortify...
My "expansion finished" timeline tends to be in the middle/late reneissance: on Monarch and giant-ish maps by this time I should have 15~25 cities , most of them near or at happy cap and up-to-date with buildings and improvements. Garrisons are in place, an army is available to respond to revolts or foreign invasions.
This is the time when the "meta" of the game definitively changes from "reactive" to "proactive": in the early game there's always a foreign invasion or a race to a wonder or something that forces me to adapt my actions/decisions around it. Now I'm the one deciding when and whom to invade, probably also tech leader or on par, and choosing my wonders and techs.
So what to do? Have a look at the map and at the diplomatic relations table: is a friendly civ about to be eliminated by an unfriendly bigger civ? Interfere! Not even necessarily by openly warring against someone , might just spam irregulars and gift them (and some money/resources) to the friendly civ to save them from destruction (later on , gifts might include obsolete (for me) units, defensive machineguns...)
Want a resource only unfriendly/overseas civs have, and they don't trade? Or want to aggressively spread your religion (Islam is perfect for this)?
Invasion!! But this time without long term occupation: conquer enough of their cities to force a capitulation, accept the vassal (if you have vassals active and if you really need those resources), or just their surrender (peace treaty), then "liberate" the conquered cities back to the original owner: liberation is a +1,5 diplo bonus, chances are a former enemy will become pleased and willing to trade.
Plenty to do at any time, just at some point it's you that need to decide for yourself what will happen.
And then, when you're so busy managing your first overseas invasion with line infantry and merchantmen, the game will surprise you with something unexpected.
Your own tech rate isn't bad either, 12 turns is pretty fine for realistic speed during the industrial age, although your cities still have significant growth potential if you give them more food from tiles, which would probably speed up the rate a fair bit more. To me it looks like there was some sort of global slowdown at some point during the game and now the tech rates are alright again?
no matter how alike they might seem, I've done that mistake many times in the past just to get the game shoveling **** to my face, and I must admit sometimes I still do. RI requires a different strategy, to open your mind for a whole new world of opportunities. Most things still work, at the end of the day RI is no more than a massive development over the base that BTS (and actually Warlords, if I recall) was, but many things require learning new appliances to pull stunts the size of what you could do back in vanilla.
We could argue that all victories are domination to a certain extent, but my point is that Domination is just brute force
, and it takes long to achieve success down that path.