You can already see the gap opening up, and the contacts color changing. As the voltage drop increases across those contacts you are going to get heating. Heating will cause warping of the metal and loss of spring action causing more drop and more heating. This will eventually result in melted material around the terminals. This is something that should be checked on a preflight. Remember not just the loss of equipment, possible damage or injury, but a fire in flight is a NTSB reportable criteria. Not worth the risk for a $115 dollar battery.