After 20 years of use the possibility is more could go.
Spokes do have a finite life and it is decreased if they are not kept properly tensioned. Loose spoles will fail much sooner than properly tensioned ones.
Carry a proper fitting spoke wrench and a broken spoke can be compensated for temporarily to allow finishing your ride.
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Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro
Visit and join the Yahoo Geared Hub Bikes group for support and links.
http://groups.yahoo.com/group/Geared_hub_bikes/