I believe that all of your replies are great! While thier values change just a little to me as I age, they still remind me of youth. The are always a prime source of mental and physical therapy when building them. I also find that they help me grow in a safe hobby (new kits, new techniques, forever learning). I would also add that it gives me another means of communication and comradrie (forums, local hobby shops, local IMPS chapter, model shows, etc.). As far as building subjects, some are from previous experience (past ownership of the real thing, past military experience, admiration of the real item, and so on..). If it is something I like but will never be able to own the real thing. In memory of friends who flew them, drove them, sailed them, etc.
How long do I keep them? For me it depends on the model. If I am please with the results and it holds some personal value to me, I keep them a very long time. It is also fun to look back on kits I built every 10 years or so to see if I notice any modeling (skills) improvement. If I have regrets about the build or the kit did not live up to my expectation in quality (or if a new release of the same subject is much better), I will either give it away, sell it, donate it, or use it for parts (after the newer one is built of course).
There are times when I see an event such as racing (NHRA, NASCAR, Rally, Endurance, F1, Indy, etc.) and it instills such a strong memory that I want to build a kit to remember it. Another instance was when I was assigned in the Operations section of a Cavalry squadron. I got to take our assigned USAF Forward Air Controller (FAC) out and watch him call in different birds like an A-10, F-16, and such. That was a thrill I will never forget. Thanks to modeling I have scale replicas of those and other craft to remind me.
All of your reasons are good, I'm just adding my 10 cents worth...
Ben
"Everyones the normal until you get to know them" (Unknown)
LAST COMPLETED:
1/35 Churchill Mk IV AVRE with bridge - DONE
NEXT PROJECT:
1/35 CH-54A Tarhe Helicopter