Someone is getting confused here on MS's end. For adding/removing phones from your Windows Phone account, there are no waiting periods at all. There is only a 5-device limit. Before I jumped in this thread, I deleted 2 phones and added one new one (which was giving me the "limit" error). I didn't even have to soft reset the phone, it just started downloading my apps. Hard resets are never required or needed (unless you're changing your Live ID, of course). I do this a few times a month with no issues. Always have.I'm trying to install apps. I got a warranty replacement for my 1020, and started getting this error. I contacted MS Support and they first suggested I delete every phone from my account, and do a hard reset on my phone. Guess what that meant? Deleting all the phones from my profile deletes all associated backups, and I have a 1020 that I can only use to make calls since I can't install any apps.
For Xbox Music, there is 30 day limit with only 2 devices being swapped out. THAT is what it sounds like they are talking about, erroneously, in this situation. It's also true that they can't bypass it. They used to be able to on Windows Phone 7.x days, but once Zune became Xbox Music, they lost that functionality. Even I can't get them to bypass that, (but the new Xbox Music app works around this, somehow).
Regarding your specific situation, honestly I have no idea. Something is wrong with your provisioned account or Microsoft ID. There is no waiting period for adding phones to your WP account. And unless you had 5 other Windows Phones registered and you wanted to add a sixth, there should be no limit/error messages at all. Yet you only had the 1020, 928 and 925 on there (three devices), which means you should never have hit that wall in the first place.
So something is very wrong here. Frankly, I don't know what will even happen past 30 days as that should not be a factor at all in this situation. You are using just one primary login for Live/Microsoft ID, right?