Your 4th year may be the charm. I had several AP trees a few years ago but all were killed by "fire blight". It took about 4-5 years for some pears to be harvested (a couple of dozen, but the trees didn't last much longer for me). My reg pears suffered FB too but survived with many wounds/scares.

footnote on the fire blight, for my trees it seemed to spread from bloom/clusters that didn't pollinate, usually from a late freeze here during bloom time. I wish I had learned this earlier to help save the trees, removing spent blossoms from the reg pears helps prevents the spread. Trimming off dying limbs didn't save the APs. Hope yours do well!