How long does your dog spend denned every day?

My dog (9y/o) has this dog house that i bought for his birthday as his 'own room' since i live in one bedroom apartment. Its inside my apartment and has three parts to it. One part has his bed in a dark den, one part is a place with pee pads for him to pee, one is for food and drink.

The only time i lock him in is at night because he marks sometimes. Otherwise its open.

The thing is, he loves his house to the point where unless hes going for walks, going to the toliet, or playing with his toys, hes in his house. He likes to spend maybe an hour in one of his other day beds in the morning, usually the one next to my desk while I do morning meetings, and has an hour cuddle session on the couch – but nope otherwise he just chills in his house. Sometimes its a total or 15-17 hours a day (including his night time stint).

Honestly i feel awfully guilty about it, even though he loves it i feel like he should be chilling around the apartment or on the balcony more. I walk past the house sometimes and see him looking out of his window in his little dark room and I get so sad. Does anyone else's dog just like dark cosy spots and should I encouraging him to spend more time outside of it?

Thanks in advance.