I have had the free version for a while and the “delete scan logs older than” and “delete temp scan logs older than” boxes keep getting checked. I uncheck both and somehow they get checked. What can cause this, can updates reset default settings?

They are checked by default, so perhaps as you suggest an update may reset it.

Are you running avast as a limited user ?
That may be something else which could restore any changed settings.

Though my question is why wouldn’t you want avast to do some housekeeping. It may well be a better option to increase the number of days that the data is retained.

I have my “Delete scan logs older than” set to 30 days and “Delete temporary scan logs older than” set to just 1 day. I can’t recall what the defaults are but you could set them to 60 days and 7 days respectively and see if that sticks.

I like records of past things no matter what is about. I checked the boxes and put 60 and 30 days in, I’ll see what happens. If it is the updates resetting settings this should not happen, updates should never default settings to any program.

It should not provided you’ve saved those settings.
As a precaution, I always save my settings which makes restoring them a lot easier.

My settings have always been honoured in program updates from the avastUI. But as Bob said it doesn’t hurt to save your settings.