You have to allow 5 working days , so not including Sat & Sun, before you can send a 'not paid ' notice by ebay . If it has not been paid for by that time send an ebay not paid notice. Don't bother sending reminders let ebay do it.
I find about 30% of people do not leave feedback, I often get feedback weeks later as you can leave feedback up to 90 days after the sale date. Like you I find that if there are problems you hear right away, no news is good news.
I do see some listings that say something like , I leave feedback , please do the same, but I never mention it.