Thanks, LarryHN. The photos are all stored on my iMac's hard drive, not on an external drive, except for the properly formatted backup drive I use with Time Machine. Thanks also for the informative link for safe storage.
I suppose this is really not a big problem. I did, however, after receiving your help, reload two photo albums I had already loaded earlier today. One of them loaded directly, the other went through the updating process again. So, it would seem to be a bit random. I will start keeping track of when it does this updating more than once.
I haven't had problems (yet) with having multiple libraries. There is a "system library" where I put things that I want to sync with my iPhone and/or iPad. My process would probably be considered to be a work-around, but so far it does work. I'd appreciate knowing what the drawbacks are as I really don't want to lose photos.
Thanks for your help.
MNorgrove