Then what would you do when you needed to reduce inflation? The Fed can sell of the assets it's bought, but the government can't sell the roads it's built.
You change the ratio independently of the budget timeline just like the fed adjusts the it's rates.
BTW you seem scared of inflation, inflation has been running low except the upper areas of the economy where the Fed has over low rates - so stock prices are inflated. What is really needed is injection of easier flowing money from below the economy.
If you invest in good programs then they deliver a positive benefit to the economy over time. Like more roads means easier connectivity, less time spent in traffic, or increased network flow. I'd suggest the biggest bang for the buck is universal healthcare and paying public college for all.
