I'm not sure if this is the right place to look for neutral, unbiased opinions, but it is a GREAT place to find convincing rationalizations and time tested arguments and strategies! So you definitely came to the right place!
I'm looking at the fleet in your signature, and it does not look at all unreasonably big. Also, the rockets themselves are not big. Once the rockets start approaching the size of humans, that's when the trouble starts. Get one that's five feet tall and as thick as your leg. At that size, it's reasonable to say maybe you can only store two or three. But for the smaller rockets, you can definitely justify more of them!
Also, rockets don't last forever. So you need to have the replacement queued up in case one crashes, explodes, or drifts away. And as you get into larger motors, you'll need to have replacements and backups ready for each level --- LPR, MPR, HPR level 1, HPR level 2, etc. --- at least a couple built kits and one on deck for each.
One of the things I've found is that my wife is not that opposed to the number of rockets and related paraphernalia as long as its not intruding into all other areas of life. So if you need a storage solution, then maybe a plastic storage bin would be a better strategy than a display on the mantel. We have a table in our garage where I like to do my builds, and my wife likes to refer to the table as the "laundry table," while I prefer to call it the "rocket factory." Now I tend to keep that term for my private use and just build my rockets on the laundry table and clean it up when done. The idea that we had a rocket factory in the garage seemed to be contributing to the idea that I had lost my mind, and the rocketry had gotten out of hand.
You gotta know when to hold 'em
Know when to fold 'em
Know when to walk away
Know when to run.
You never count your rockets
When yer at the laundry table
Open up yer rocket factory
When she's gone to bed
