Had a few "bits" through my hands over the years but I only ever regretted one sale:
1992 - The complete UK Motown catalogue (including the London, Fontana, Oriole, Stateside 45s and two copies, demo and beautiful green stock issue, of The Spinners on Columbia). NEARLY ALL on demos where applicable. AND in relevent company sleeves. No wol, sol, all with centres.
Took me about 17 years. Couldn't do it nowadays. It'd be impossible to start again. You'd have to sell body parts.
About 10 years ago in a fit of remorse, I set out to do the US catalogue. (Has anyone actually done that UK and US?) I gave up after about 6 years. Too overwhelming.
Still...enjoyed putting it all together and have most of the UK items I had on US Demos now.