how to keep numbers older than 30 days

Your recents are not tracked by date. Instead, your recents list is of the most recent 100 calls. When you reach 100 calls on the list, the oldest will drop off when you receive the newest call.

If you need to see calls no longer visible on your iPhone, you can contact your carrier, or log into your carrier account, where you usually can see call logs for your cell number.

The amount of time isn’t the issue ( I still have some in my call log from years ago) but as more calls come in if you don’t remove some of those newer ones they will push out the older ones.