Got a bunch of solder . . .

[Petrol & Powder]

Silver solder is good for high strength repairs, As Ian points out.
That stuff is expensive but sometimes very useful.

I wouldn't waste that in some lead alloy for bullets.

 

[Snakeoil]

I thought I read somewhere that Solder goes bad after so long.

It is solder joints that go bad with time. That's why antique brass instruments, no matter how special never achieve true collector type pricing because they inevitably will need a total disassembly and rebuild at some point.

Yes, all that solder is junk. I'll give you my address and you can send to me and I'll dispose of it for you for free.