I wish I had combined my second contract with my first when I acquired it. I started the process a few weeks ago to combine them, but WM takes FOREVER to do simple things like send paperwork for combining accounts! I am combining my September use year into my July use year. I have given them 6 months to get this done so I better not lose credit due to WM horrible customer service.
As I recall, the combine rules changed to something like, "Combines will not occur until the credits for both ownerships have been awarded for the (calendar?) year." (The intent is obviously to eliminate "advancing credit awards," which it sounds like your combination would do.) If that is the case, your combine may be delayed until after your September anniversary. Or worse, since the process will be so far along by July, the accounts might be combined sometime after your July anniversary and before your September 1 award, which would mean a 10-month delay in your next September, 2024 (to the then, combined July, 2025) award.
I purchased an account with a July anniversary in November 2019 to combine with my account with May anniversary. The combine paperwork was requested in Nov 2019. Wyndham sent me paperwork to sign in February 2020, which seller and I promptly returned. Wyndham took no action on this paperwork...
tugbbs.com
The reason for the rule change was, as usual, wiseguys abusing the system -- in this case, repeatedly buying a small account to combine with a much larger account and "advancing" the credit awards of the ever larger and larger accounts time-after-time-after-time -- essentially creating credits out of thin air. It was a corrosive scam. I think Wyndham made the perps pay for their ill-gotten credits, to the extent possible.
I learned a lot from that thread (TUG is the Best!). That is why I recently combined a July Anniversary ownership with an August Anniversary ownership, timed to complete in November (before the end of the calendar year), which it did. The July award will now occur 1 months later every year going forward -- no big deal.
I have a February and August anniversary memberships that I wanted to combine, but did not want an adverse combination timing. I found a great deal on an August anniversary to combine into the existing August anniversary, and will just sell the February ownership. The $399 transfer fee is much better than possibly delaying 6 months (or up to 18 months of credits, and losing 6 months worth).
It is all in the timing. Let us know how it turns out for you, to add to the excellent TUG wealth of information.