An apple and pear combination will not be any sweeter since both juices will ferment to dry if left to their own devices. If you want a sweet cider or pear cider you need to either cold crash at the desired level or backsweeten and stabilize.
If anything, over time, more flavor develops . . . to a point. Three weeks won't have any negative effect.
In all the states no door stands wider,
To ask you in to drink hard cider