The L-1A nonimmigrant classification enables a U.S. employer to transfer an executive or manager from one of its affiliated foreign offices to one of its offices in the United States.

For all L-1A employees, requests for extension of stay may be granted in increments of up to an additional two years, until the employee has reached the maximum limit of seven years

Are they really using this more than H1B? Doesn't sound like it, but I guess it is possible.

https://www.uscis.gov/working-in-the-united-states/temporary-workers/l-1a-intracompany-transferee-executive-or-manager