1996 Tahoe won't stop quickly

I am the original owner of a 1996 Chevy Tahoe with 137,000 miles on it. My concern is that the vehicle cannot brake quickly. I can come to a normal stop but to brake quickly - in the case of preventing an accident the vehicle doesn't seem to be able to stop. I cannot lock the tires up at all. I recently have had an accident because I was not able to stop in time.

The rotors and pads have been replaced numerous times but my ability to quickly stop has not been an option. I recently purchased a 23ft boat and plan on towing it with this vehicle. I'm concerned about my ability to stop when adding additional weight to the vehicle.

I would appreciate any thoughts. Thank you.