Back sweetening, extra sorbate question

[TemperanceOwl]

Last year I made the WinExpert Chocolate Raspberry Dessert Wine per the instructions, and bottled a year ago today. It comes with an f-pack, which I added after adding the potassium sorbate and k-meta.
The final SG after adding the f-pack was 1.016, and I don't find it sweet enough for a desert wine.
I am going to add invert sugar to raise the SG up to 1.064, or 16 brix.
Do I need to add more potassium sorbate since it's been a year since I added it, or does it remain effective forever? I definitely do not want to induce any weird off-flavors, but I also don't want a sticky eruption.
Thanks for your advice!

 

[salcoco]

based o your remarks the original addition did not cause a fermentation. I would assume any additional sugar would also keep the wine dormant without addition of sorbate.

 

[TemperanceOwl]

Thanks, Salcoco. That's what I was thinking, but wanted another opinion. I know Kmeta evaporates over time and loses its potency and wasn't positive that sorbate doesn't do the same thing.