Paddy, when using this feature, and since you mentioned using "too many tapes", keep in mind though you are combing Copies to a single destination Policy, the retention for each job is still respective to the source Copy. This is important to keep in mind that jobs could be held long than expected for some tapes and those tapes will not return to scratch until all jobs meet retention (general rule of thumb for retention).
Copy 1 Retention - 30 Days 1 Cycle
Copy 2 Retention - Infinite
Global Secondary Copy - if jobs from Copy 1 and Copy 2 write to the same tape, that tape will no be returned to scratch even if Copy 1 jobs meet their retention. Hope that makes sense.
So having said all that if you do use it, just be mindful of what your expectation will be, its really good for those long-term retention copies which you may never recall or have infinite retention or long-term retention spread across copies.
Another option you have to consolidate tapes on a copy is to use this feature as well, it will maintain jobs on the existing copy.