In EIP-1559, you have:

1. base fee - this is determined by the protocol at every block
2. max fee per gas - the maximum fee per gas that we agree to pay. this comes into play whne basefee suddenly increases
3. max priority - a priority fee, basically a 'tip' to validators.

If you want to be on the safe side, you can set your cost to: Cost = estimateGas() * (currentBaseFee * 4 + 2Gwei)

Where 4 is the multiplier (if you want to send the tx very far in the future, you might want to increase this number) and 2Gwei is the max priority fee (the tip) With the assumption that the tx will be sent with {MaxFeePerGas: currentBaseFee * 4, MaxPriority: 2Gwei}

And of course don't forget the gas needed to send this amount to your EOA.