Welcome to the forum.
You question is a good one, which unfortunately has no hard and fast rule. Most women are off the labetolol with in a few months but for some it can take longer (or for a few even less!)
Generally speaking most women are back to their pre-pregnancy selves within a year or less.
I hope this helps
Every Woman is entitled to understand what happened in her pregnancy when pre eclampsia strikes. I hope to be able to support that process.