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.
+ HelpExampleRpc("getwalletinfo", "")
        );
    ObserveSafeMode();
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK2(cs_main, pwallet->cs_wallet);
    UniValue obj(UniValue::VOBJ);
    size_t kpExternalSize = pwallet->KeypoolCountExternalKeys();
    obj.push_back(Pair("walletname", pwallet->GetName()));
    obj.push_back(Pair("walletversion", pwallet->GetVersion()));
    obj.push_back(Pair("balance",       ValueFromAmount(pwallet->GetBalance())));
    obj.push_back(Pair("unconfirmed_balance", ValueFromAmount(pwallet->GetUnconfirmedBalance())));
    obj.push_back(Pair("immature_balance",    ValueFromAmount(pwallet->GetImmatureBalance())));
    obj.push_back(Pair("txcount",       (int)pwallet->mapWallet.size()));
    obj.push_back(Pair("keypoololdest", pwallet->GetOldestKeyPoolTime()));
    obj.push_back(Pair("keypoolsize", (int64_t)kpExternalSize));
    CKeyID masterKeyID = pwallet->GetHDChain().masterKeyID;
    if (!masterKeyID.IsNull() && pwallet->CanSupportFeature(FEATURE_HD_SPLIT)) {
        obj.push_back(Pair("keypoolsize_hd_internal",   (int64_t)(pwallet->GetKeyPoolSize() - kpExternalSize)));
    }
    if (pwallet->IsCrypted()) {
        obj.push_back(Pair("unlocked_until", pwallet->nRelockTime));
    }
    obj.push_back(Pair("paytxfee",      ValueFromAmount(payTxFee.GetFeePerK())));
    if (!masterKeyID.IsNull())
         obj.push_back(Pair("hdmasterkeyid", masterKeyID.GetHex()));
    return obj;
}
UniValue listwallets(const JSONRPCRequest& request)