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.
}
    }
    
    if (listReceived.size() > 0 && wtx.GetDepthInMainChain() >= nMinDepth)
    {
        for (const COutputEntry& r : listReceived)
        {
            std::string account;
            if (pwallet->mapAddressBook.count(r.destination)) {
                account = pwallet->mapAddressBook[r.destination].name;
            }
            if (fAllAccounts || (account == strAccount))
            {
                UniValue entry(UniValue::VOBJ);
                if (involvesWatchonly || (::IsMine(*pwallet, r.destination) & ISMINE_WATCH_ONLY)) {
                    entry.push_back(Pair("involvesWatchonly", true));
                }
                entry.push_back(Pair("account", account));
                MaybePushAddress(entry, r.destination);
                if (wtx.IsCoinBase())
                {
                    if (wtx.GetDepthInMainChain() < 1)
                        entry.push_back(Pair("category", "orphan"));
                    else if (wtx.GetBlocksToMaturity() > 0)
                        entry.push_back(Pair("category", "immature"));
                    else
                        entry.push_back(Pair("category", "generate"));
                }
                else
                {