If I unlock an encrypted wallet for 359711509437336256 or less seconds, I can sign transactions with it:

    $ bitcoin-cli walletpassphrase "$x" 359711509437336256
    $ echo $?
    0
    $ bitcoin-cli signrawtransaction $tx | grep complete
      "complete": true

But if I unlock it for 359711509437336257 or more seconds, it appears to have unlocked but I can't sign any transactions:

    $ bitcoin-cli walletpassphrase "$x" 359711509437336257
    $ echo $?
    0
    $ bitcoin-cli signrawtransaction $tx | grep complete
    error code: -13
    error message:
    Error: Please enter the wallet passphrase with walletpassphrase first.

I don't know the significance of that number. It's nowhere near a power of 2.

I was trying to unlock the wallet effectively "forever", so put a big number. If I use too big a number (2^63 or more) I get an error message `JSON integer out of range` but for numbers between 359711509437336257 and 2^63-1 inclusive I get no error, but no actual unlocking.
}
    CBlockIndex *stopBlock = pwallet->ScanForWalletTransactions(pindexStart, pindexStop, true);
    if (!stopBlock) {
        if (pwallet->IsAbortingRescan()) {
            throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
        }
        
        stopBlock = pindexStop ? pindexStop : chainActive.Tip();
    }
    else {
        throw JSONRPCError(RPC_MISC_ERROR, "Rescan failed. Potentially corrupted data files.");
    }
    UniValue response(UniValue::VOBJ);
    response.pushKV("start_height", pindexStart->nHeight);
    response.pushKV("stop_height", stopBlock->nHeight);
    return response;
}
extern UniValue abortrescan(const JSONRPCRequest& request); 
extern UniValue dumpprivkey(const JSONRPCRequest& request); 
extern UniValue importprivkey(const JSONRPCRequest& request);
extern UniValue importaddress(const JSONRPCRequest& request);
extern UniValue importpubkey(const JSONRPCRequest& request);
extern UniValue dumpwallet(const JSONRPCRequest& request);
extern UniValue importwallet(const JSONRPCRequest& request);
extern UniValue importprunedfunds(const JSONRPCRequest& request);
extern UniValue removeprunedfunds(const JSONRPCRequest& request);
extern UniValue importmulti(const JSONRPCRequest& request);
extern UniValue rescanblockchain(const JSONRPCRequest& request);
static const CRPCCommand commands[] =
{