Looking at your first image, you have a gap yes, I don't know if this is time zone related or not as I'm in the UK and Avast is the Czech Republic. Although that would account a bit for time differences in our images, the actual streaming updates version numbers would/should be the same. But compare your last one with my 21030406_stream and there is roughly a 12 hour time difference.
That said over and above actual virus signatures there are other protection features. Behaviour Shield, Cyber Capture and Hardened Mode, which aren't dependant on signatures alone. Unknown file or behaviour etc. would result in an on-line check.
Personally if I were in your position, I wouldn't be unduly concerned.
Though if you haven't done a system restart in a while I would do that