I'd like to take this opportunity to welcome you to the forums, and apologise for the delay in getting to your post.
Should you wish to permanently disable the power saving setting, (this is the feature that will put your TiVo into standby after 4 hours of non use), then just follow these commands on your remote
Home > Help & Settings > Settings > Devices > Power Saving settings
You will see there are a few options, just move the tick to the "Always on" position.
Should you wish to leave the Power saving settings as they are, and just wish to clear the on screen message when it does pop up, I believe if you just hit the TV button on your remote it should clear the message and restart the 4 hour countdown. However it's been some time since I have see this message myself.