Right from GC's policies:
Returned items must be in original, brand-new condition and show no signs of wear or use including, but not limited to, belt-buckle or pick scratches, scuffs, dings or scrapes on the instrument or collateral materials. Items must also include all original packaging, manuals, warrantees and accessories or your return may be subject to a return handling charge.
Abuse of Return Privileges
Our return policy is in place to ensure our customers don’t get stuck with the wrong piece of gear. We may, in our sole discretion, limit or suspend return privileges for customers who abuse or attempt to violate our return policy through practices including, but not limited to, excessive returns, attempts to return items that are no longer in brand-new condition, etc.
Sounds like they track a customer's return history, so you can't use their return policy like a free rental. There is nothing about not gigging with a potential return. My guess is that if you do take the amp out to a gig better not let it get dinged or scratched if you want all your money back. If I buy an item for bass, I am taking it out on my next gig and if it doesn't cut it, it goes back. I guess mainly it comes down to intent. Personally as a gigging musician, I can't imagine owning only one amp. One of anything actually. I have had problems with my gear that I was able limp through the current gig but had to be switched out for the next days gig.