Expired points

After my bill is paid or I rent a movie, it sometimes takes weeks for my points to show up in my account. I don't look often at my points but I noticed that in July and August that over 200 points had expired. There was no warning or else I would have made sure to use them. Is there any way to get these back? I often use the OnDemand so this is super frustrating that it takes so long for points to show up but then they expire with no warning.