I don't know if it's really a good idea to use USB sticks for that, I would have made a paper wallet and laminated it. You say you burried it? What if moisture reaches those USB sticks and they don't work anymore? Not saying it's a bad idea to put your savings into Bitcoin, but I think you could have done it in a better way.
I don't think laminating a paper wallet would necessarily be a good idea either, as the lamination could start to peel or wreck the wallet in another way, and it would require more effort to be put into it in order to make sure that it all comes out fine and the Bitcoin is recoverable, as opposed t a USB.
I'm not saying a USB is amazing either, but I think it is better than a paper wallet being buried underneath the ground and expecting it to go well.
true, the lamination could cause trouble so maybe a waterproof, fireproof, tamperproof, earthquake-proof double insulated reinforced hardened titanium vault/safe could do the trick and then you put both laminated and unlamented paper wallets inside so incase the 'waterproof' proofed to have a tiny little leak and say there's a flooding then the paperwallet with the lamination might just do the trick and the unlaminated paper wallet might be lost. Of course CD's too and maybe an expensive lifetime guarantee USB for convenience and ease of use.