On Wednesday, July 24, 2019 at 10:11:29 PM UTC-4, wrote:
Thanks for that! It's later than I expected, and if I am correctly informed, will last you indefinitely as long as you don't leave it tied out &c.

All polyester gelcoats will eventually fail. Schabbelack had a longer life than Vorgelat. Storage, particularly moisture conditions, as well as obvious UV and temperature cycle conditions, all matter in terms of aging.
Everybody wants an old economical glider with "good gelcoat". They are exceedingly rare.
Glasflugel ships had Schwabellack(not sure the last ships did) as did DG.
FWIW
UH