How long walking a cat is too long?

TL;DR: My cat ended up walking for 1.5 km almost daily. Is it too long?

Due to some renovations in my apartment, I had to move to somewhere 1.5 km away only for two months. My cat, which was a stray cat who decided to live with me, couldn’t come along to my temporary apartment. I stopped by my old apartment daily and contacted others who pet him when he is around to take more care of him.

However, after feeding, he started following me to my new apartment. I never touch or carry him, he follows me on his own. He gets scared sometimes but still follows me. I also take him back to his own turf where he is familiar with the surroundings in the morning.

This way, he ends up walking at least 1.5 km daily. He hasn’t followed me every day so far, so if he does, he will be walking 3 km. Is it too much, assuming that I am monitoring his weight?

Some details: he is 6 years old, unknown breed – probably not a pureblood, large and relatively chonky. He weighs 6.5 kg and has a tendency to overeat.

When I am done with my studies, I will move to some more permanent and cat friendly location.

Thanks in advance!