Not a big concern, few people who make an effort to use a standing desk are going to end up standing for too long, as they will take breaks (get a stool). It's

Not a big concern, few people who make an effort to use a standing desk are going to end up standing for too long, as they will take breaks (get a stool). It's far more likely the average person will sit too long since the symptoms of excessive sitting only appear later on; the actual time of sitting will feel comfortable and people go 9 hours a day without taking a break.