The vintage kits I buy I generally build unless they are really rare.
I have a Vintage K-29 Saturn 1B and a K21 Gemini Titan that I was going to build, but now will not seeing as the S1B is cloned by Semroc and the Gemini by PD Rocketry.
I currently have an opened Enerjet Nike Smoke with "working" smoke that intend to build....that one IS really rare,but has little value as it is opened.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !