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.
"\nExamples:\n"
            + HelpExampleCli("listaddressgroupings", "")
            + HelpExampleRpc("listaddressgroupings", "")
        );
    ObserveSafeMode();
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK2(cs_main, pwallet->cs_wallet);
    UniValue jsonGroupings(UniValue::VARR);
    std::map<CTxDestination, CAmount> balances = pwallet->GetAddressBalances();
    for (const std::set<CTxDestination>& grouping : pwallet->GetAddressGroupings()) {
        UniValue jsonGrouping(UniValue::VARR);
        for (const CTxDestination& address : grouping)
        {
            UniValue addressInfo(UniValue::VARR);
            addressInfo.push_back(EncodeDestination(address));
            addressInfo.push_back(ValueFromAmount(balances[address]));
            {
                if (pwallet->mapAddressBook.find(address) != pwallet->mapAddressBook.end()) {
                    addressInfo.push_back(pwallet->mapAddressBook.find(address)->second.name);
                }
            }
            jsonGrouping.push_back(addressInfo);
        }
        jsonGroupings.push_back(jsonGrouping);
    }
    return jsonGroupings;
}
UniValue signmessage(const JSONRPCRequest& request)