I still have my first love (a black Brain Bag) going on 12 years now. All my TB's are going to be heirlooms.
Shortly after I gave my Olive/Solar Synapse to my spouse, I was seized with longing and regret. The Smart Alec I had purchased to "upgrade" capacity did not elicit the same feelings of delight . After a few months of use, I certainly did develop respect and appreciation for it's design, superb quality and capacity. My spouse consented to acquire a new Synapse ( Black/Iberian) and return mine. Yes! I now switch off between both bags. If I acquire the larger Synapse should I sell the Smart Alec? Perhaps I need carefully consider this tale of remorse before acting rashly.
My own experience isn't quite so drastic: I purchased the Imago a year ago or so and, while well-made and all that, not really laid out well for my needs at the time. Thankfully, I did not get rid of it, though the thought did cross my mind (as in, "hmmm, perhaps I should sell this to fund some new TB loot"). A few months ago, I pulled it out thinking I'd give it another go...and lo and behold! It's my fave of the moment! It's laid out perfectly for my needs right now.
Am I suggesting one should never part with TB gear? No, of course not. But, I guess, proceed with caution when parting with your TB "family" :)