Mindfulness meditation practice is not a competition, with yourself or anyone else, to try to spend as long as possible with no thought.
The benefit of the practice of mindfulness meditation is the process of bringing your focus back from your compulsive background thoughts so each time that you do that you progress in your mindfulness practice.
Experienced meditators with any honesty admit their thoughts intervene. Experiencing compulsive thought and refocusing ‘is’ the practice so while that happens you’re doing fine.
An example I use is learning to ride a bike. It’s the falling off that actually teaches you how to ride. With mindfulness meditation it’s the practice of continually releasing your thoughts that enables you to be mindful in everyday life.