How important do you feel full stops (periods) are in your ads? or do you not bother with them at all? Im thinking if your ad appears at the top of searches (not at the right) then maybe a full stop comes in handy there to slightly seperate the two parts of the ad description.
If you're also using search network and/or content, remember that the 'layout' of the ad is often different to the way it look in serps sponsored listings (i.e the way it look when you type it into adwords), so having a proper sentence, with punctuation can be vital to ensure it makes sense. (someone once posted on here a thingum they'd come up with to automatically show the ad in the different versions it can show up in different searches, but I can't find the link)
Ive not been putting .'s in until i was thinking about it tonight and added a couple to an ad, a few days ago when i was using the preview tool and it showed the ad at the top (not right position) i noticed how missing full stops could sometimes mean the description doesn't read as good as it could. And you pointing out the fact that theres a difference of how the ads look on content network to search network is something im glad you have mentioned too, i hadn't considered that enough, not used the content network yet but no doubt will at some time.