I don’t believe that you can overdo it with liquids, but this all depends on what you’re intending on doing with your boilies. Most who follow my angling exploits will know I’m a huge fan of using liquids in my mixes, and this is for several reasons.
First, I love to over-saturate my boilies to make them very dense. I then use them in my mulched-up mix. The liquid content makes the crumb really heavy and ensures it reaches the lakebed while also releasing attraction as it makes its way down. Once on the bottom, it makes the baits very soft and even easier to digest throughout the seasons for the carp.
On the flipside, if you’re looking to use boilies with a different delivery method, such as a throwing stick, then using too much liquid in the bait will just force the boilies to split as they travel through the air. In this instance, I’d only use a light coating of liquid, just to lubricate them so they fly through the stick more easily by creating less friction against the carbon.