Suddenly realizing that many people are worried about being laid off once they turn 35 seems to be pure anxiety.

Most layoffs in many companies involve administrative and technical positions—roles that don't directly generate revenue for the company.
But sales positions, which are responsible for bringing in money, are generally less likely to be cut.
As long as your performance is outstanding—if your sales figures can match or even surpass those of a small team or half a department—you become the company's key asset. When you want to leave, the company will even offer higher salaries to keep you.
Even if your performance is average, as long as you're not consistently at the bottom, you can stay in the company for a long time.