Leaving a laptop in sleep mode for about 8 hours while using it occasionally should not have a significant negative effect on the battery life.
When a laptop is in sleep mode, it uses very little power to maintain its state, and the battery should not be drained significantly during this time. Additionally, modern laptop batteries are designed to handle many charge cycles, which means they can be charged and discharged many times without significant degradation in performance.
However, it's always a good idea to periodically fully shut down your laptop and give it a chance to rest and cool down. This can help to prolong the lifespan of the battery and other components.
It's also worth noting that if your laptop is in sleep mode and not connected to a power source, the battery will continue to drain over time, even if it's not being used. If you plan to leave your laptop in sleep mode for an extended period of time, it's a good idea to make sure it's fully charged before doing so, or to connect it to a power source to prevent the battery from draining completely.