Litterbox question for inside / outside cat

I would like some advice, here....

Guinness has been an inside / outside cat now for about 1 year. I keep him inside at nightime. He has got into the habit of knowing that it is bedtime and he will come in and climb straight in his bed (or my bed!) He has a clean litterbox available for him to use during the nightime.

However, the past 4 months he has not touched his litterbox. I think that he is so used to his routine that he gos to the toilet before he comes in. In the morning, he never seems desperate to go outside either, he will wait for food and hugs before he gos out.

Do I take his littler box away from him seeing as he does not use it anymore?

I would keep it around, you never know when he might need it and better to have it than find out he had an accident.

Would he meeeow if he needed the toilet? My parents have kept cats for years now and before they had a cat flap fitted, if the cat was in a bedtime then it stayed in all night. They never used litterboxes...

I have indoor outdoor girls( aka the back yard) and three boxes two get used regulary and one just got used the first time in about three weeks so I would keep it