Glad you're keeping him in a bit longer.
In South Africa where I grew up, we had two wonderful cats, Cinder and Sasha (Lexy is her namesake). When my mum and I decided we were moving to the UK 15 years ago, we had a very difficult decision to make. Cinder was 10 at that point but Sasha was already 17. We decided that my sister, who was still living there, would take them so that they woulnd't have to go through 6 months of quarantine. We knew that Sasha would never make it if we did.
So we took them to my sisters and off we came here. Then about 3 months later I got a letter from my sister. She didn't have the heart to call me and tell me and thought the best way to pass the news was to write it. My sister was heartbroken. The cats had lived outside and inside for more years that we could think of. They were not happy kept in. Sasha though being an old lady and a queen mind you loved nothing more than the cuddles she would get indoors so she didn't mind.
Sasha was fine, she lived a long happy life with them until sadly she passed away at the ripe age of 21.
Cinder however, they let out after only a couple weeks because she implored them. She didn't like being cooped up my little baby, so my sister caved. She came back after an hour or so. But then the next day she went out, and they never saw her again.
Their posters, continuous driving round, knocking on neighbours doors proved fruitless. Cinder was gone. My sister went out each day early in the morning and when she got home from work for two weeks solid, nothing. It took my sister two and half months to tell me, she was so devestated. Sasha mind you seemed happier (Cinder was a right little scrap who annoyed Sasha no end).
If you're in doubt keep him in. The heartbreak is awful. It took me 15 years to want to have a cat again, I coulnd't bear the pain of losing my baby.