Gas follows block-space demand
On Ethereum mainnet the base fee rises when blocks are full and falls within minutes when they are not. Quiet windows are typically outside overlapping US and European working hours, and during periods without a major mint, launch or liquidation cascade.
On rollups and low-fee chains the absolute numbers are small enough that this rarely decides anything, which is itself a reason to choose the network first.
Liquidity follows attention
Pools are deepest and spreads tightest when the most participants are active, which is roughly the opposite of the cheap-gas window. Trading a thin pair at 04:00 to save a dollar of gas can cost several times that in price impact.
For a small trade on a cheap network, gas dominates. For a large trade, depth dominates and you should trade when the market is awake.
Events that are worth avoiding entirely
Major macroeconomic prints, scheduled protocol upgrades, large token unlocks and the minutes around a liquidation cascade all widen spreads and raise revert rates simultaneously. The fill is worse and the chance of paying gas for nothing is higher.
If a trade is not urgent, waiting an hour after such an event is usually free and measurably better.
The honest limit of all of this
None of it predicts direction. Choosing a cheap, liquid moment improves execution of a decision you already made; it does not make the decision correct, and the price can move further against you while you wait.
FBT Swap shows the live quote, route and fee at the moment you ask, which is the only timing information that is actually a fact rather than a forecast.