Just as a follow up to my initial post (which I realize was six months ago), I believe that I have finally got this working (not perfect but to my satisfaction at least). In some ways, it was 'better' before (sync was NEVER automatic but I could always manually sync wirelessly), but in other ways, it is 'better' now (sometimes I can manually sync but as often as not, my iTunes PC "was not available", however, it does sync wirelessly, on it's own [when on wi-fi and charging of course], several times per day). I guess it's a matter of preference which of the two scenarios is better but I'll pass on how I got auto syncing to work.
First, the many numerous articles, posts and blogs out there were all helpful in the procedures to set up wi-fi sync with iTunes (I'm going to skip all that, because as I mentioned in my initial post, manually initiated wireless sync had always worked, so the BASIC workings were in place, otherwise (IMHO), I wouldn't be able to manually wi-fi sync).
I resigned myself to manual sync (after all, not the end of the world since I'd still be cable-free). However, I had to replace my aging router / bridge combo with a new router / switch combo and suddenly found that my iTunes PC was NEVER available; so I had to sync using cable and that wouldn't do! 😉 So I had to revisit this.
In a nutshell (as I am sure everyone is bored by now), I had to do two things that I hadn't before: 1) was open the router's firewall for TCP 3689, UDP 5353 and TCP/UDP 123. There's a few articles out there on ports that Apple used for various functions but these seemed to be more specific for wireless sync. In itself, opening these ports didn't seem to do anything but I left it that way. 2) Next, I read an article post that stated that Windows firewall (if running Windows, of course) had to also be opened to allow SyncServer.exe ("SyncServer.exe is an executable file that belongs to Apple Mobile Device Support, a program that is required to synchronize devices through iTunes."). So I looked through my Control Panel / Security settings and found that I didn't have it opened. I was dubious that this was going to make any difference, but when I looked at my phone (not connnected by cable), the Sync Now was blue - EUREKA!
The Eureka was short-lived though, as I checked throughout the day (without leaving the house or wi-fi converage) and it was usually grey but sometimes blue. The next day, I looked and it was currently blue but the timestamp on the last sync was sometime overnight (when I'd be charging while asleep). That, almost a year later, was my first true wireless sync with iTunes that was not initiated manually.or by cable. Over the next few days, I would periodically check my device and it'd be grey or blue (no pattern that I could see) as I went about my business, both home and out and about. This is the 5th day and it has synced wirelessly, automatically at least once per day (I say at least once per day because I can't specifically tell when the previous to the previous sync was).
So I'm satisfied with that. Not perfect, but I'll take it.
Edit/Add: just to add one thing - many articles/blogs/posts state that both the iPhone/iPod and the device that iTunes is running on must be on the same WIRELESS network and not just on the same network (i.e. they specifically state that the iTunes PC can't be wired and the iPhone/iPod be on Wi-Fi). My PC that iTunes is running on is wired and on 24/7 (it's my streaming PC) and definitely has no wireless capabilities.
