As Russia, I find it very unprofitable to build 80% farms in most provinces, as they never make their money back. Only select provinces that definately pay back their investments get the 80% farming upgrade. Otherwise, I find I'm spending more building the farms, than the farms are producing over a wide timeframe. I build 20% farming in all provinces, 40% in the medium-yield provinces, 60% in the higher and very rarely an 80% farm upgrade. I rarely need such monetary power as I conduct all of my wars on as small a frontage as possible, and preferably one faction at a time. Although I could afford to fight multiple enemies, I can keep peace, pick on one and lower my standing armies, freeing up money taken by upkeep, and build some teched-down defence armies to plug gaps and deal with AI aggression. 8,000 men sitting in a port, waiting for the call to duty is a strong deterrant to anyone who fancies trying to grab a few of my lightly garrisoned backwater florin-cow provinces.