No, it's plugged into a Lithium Ion Battery Charger. It stops charging at full charge and starts trickle charging when the voltage drops to typically around 4.0 V. Repeats...
Plus the battery pack itself is required to have it's own protection circuitry to prevent over voltage, over current, and under voltage.
The last recommendation I read when I purchased my Vagabond Mini Lithium was that it was okay to leave it plugged in 24/7.
And that's exactly what I've been doing for months.... No problems. No issues. I keep my VML mounted on a lightstand and plugged in. VML remains at the ready, simply unplug and go!
If it was the older Vagabond models you would have trouble. But the technology is different in the mini and you shouldn't see any long term effects from this.
Not sure how its different with the older models.... I was told when I bought my original to always keep it plugged in unless I was using it and I have and I RARELY use it ever and after 4 months just used it for the first time today and shot 230 shots with a WL 1600 at about 1/2 power and no problems.
ken